I estimate that unsafe for a beginner or someone on the ins and outs of Chloro, the Warlock is the best secondary soul. Benefits are mostly passive or long term buffs ... So you are accustomed to focus on the chloro tool-set and the Chloro strengths and weaknesses. Archon and Necro are the other most common secondary souls, but both have to take more active tool sets for the contribution to Chloro and therefore require a greater choice and perhaps a deeper knowledge so that you can use the right decisions the right time to use which abilities.
For beginners, by using Warlock, you're able to focus on the Chloro abilities. You just have to get less business and are less likely to be in difficulties.
Note: Chloro healing at levels below level 15 is very different to what's described in this guide. Personally, I would only start using Chloro as your Main soul from level 15 onwards. You only need to really need to main heal from level 16 in the first instances. You can go for more at lower levels and there's some nice builds for that... but there's really little need at lower levels and there are more efficient builds.
Warlock Point Investment
Once you have Chloro/Lock as your main souls, then the Warlock tree for Chloro support is pretty straight-forward. As of Beta 6 you're aiming for it to look like this.
I've included Neddra's Influence - which is a DoT enhancement. It is believed that this affects Stream of Reclamation (SoR) damage and Withering Vines (WV) damage (but not the heal element of Withering Vines and not the DoTs from Nature's Corrosion).
There are other options and things you could extend this with... but for the basic tree, that's basically what it will look like.
Apart from the first 6 points in the Warlock tree for the mana regain tool, you'll be pouring all your available points into the Chloro tree. By the time you reached a level with your Chloromancer, that you were able to get as high in the Warlock tree as linked above, you'll be making all your own decisions about what things to take and where, primarily based on your own experiences.
It's important to let your own experiences guide you most strongly. Test what other people say in your own play and decide for yourself what is better.
Chloro Point Investment
As of Beta 7, Call of Spring isn't working on the core heals of the Chloro: Radiant Spores (RS) and Lifegiving Veil (LV) heals. Since these represent 90% of the healing that you'll do as a Chloro, that makes it a lot weaker. The Chloro Shield ability, also got a big rebuild in Beta 6 and is much stronger now, with the mana regain built in. Also, the present state of the Nature's Corrosion improvement, is that it will enable your Ruin and Vile Spores to do ~30%+ more healing (based on logs). That may be bugged like Call of Spring - and both may be fixed - but as things stand, Nature's Corrosion is a strong contender for points and Call of Spring a weak one.
As a result, most Chloro/Locks will probably aim toward a build that looks something like this, which leaves 4 points over... about which endless discussions could be had... but none of them will affect you much right now, since you'd need to be level 47 to get to those decisions pretty much.
It's important to let your own experiences guide you most strongly. Test what other people say in your own play and decide for yourself what is better.
Important Equipment
If at all possible, you should get a sigil that will take a Greater Essence and put into that slot one of the Essences that gives you a chance of proccing extra healing whenever you cast a healing spell. Lifegiving Veil heals will proc these Essences. This can add a huge amount of healing to your Chloro, as it can proc separately on every single target that your Lifegiving Veil heals hit.
Your basic priorities in casting should 90% of the time be:
Radiant Spores must be kept up.
Explain to your group, that if they're taking damage, more dps = more healing from Radiant Spores. Faster consistent hits are probably better than slow big ones in that situation (because you may or may not get that 30% roll on a slow big hit... but if you do 5 other hits in the same time, you'll probably get healed by a couple of them).
Nature's Touch is your first active healing priority.
If there's ever a choice of which active heal to cast, Nature's Touch should be your first choice. It's the best nuke for both tank and group heal.
Ruin is your second active healing priority.
Vile Spores when there's nothing else you need to be doing
Keep Entropic Veil up when you can. I personally tend to hit it when charge is up to ~50%.
Your Nukes are your Heals
When everyone/several people in the group/raid takes damage at the same time, trust in Lifegiving Veil and Radiant Spores to bring everybody back to full health. Your nukes and Radiant spores will usually do the job just fine. Most situations like this don't need a direct heal.
Direct Heals are for Emergencies
Direct Heals (Bloom/Flourish/Wild Growth) should be used when the above is all failing. They are to be viewed as your emergency heals.
Your first instinct when people in your group start taking damage, should be to hit another nuke not a direct heal. Direct heals are for when you're sure that nuking and radiant spores isn't going to work any more.
Rotations
There is no real 'rotation' for Chloros, because to a certain extent you're reacting to a situation. But the basic healing rotation should probably be something like:
Ruin, RS, NT, VS, VS, NT, VS, VS, Ruin, RS....
I put Ruin in before Radiant Spores because when Ruin recycles, I use it and know that I have to use Radiant Spores straight after it to keep RS maintained (Ruin cooldown = Radiant Spores duration - 1s). You'll have slightly different ways to lead into this rotation at the beginning and will always be making adjustments because of using your mana regen tools, Bloom/Flourish/Wild Growth etc... as well as other bits and bobs in the Chloro tool-set. But at heart, the above is the basic Chloro rotation.
Entropic Veil is a decision thing. Some Chloros prefer to save it for when they need a bit of a burst of healing. My approach is to maintain a consistently high level of healing, so that you're less likely to get into a situation when you need that burst in the first place. Also, with Warlock you get such good charge regeneration, that you will find that you swiftly get 50% charge back again - so if you do need a burst at some point, you're likely to have enough charge to give you that.
Your Chloro mantra is:
"My nukes are my heals... My nukes are my heals.... My nukes are my heals...."
Repeat it and repeat it and repeat it until you can think nothing else, young grasshopper - and you shall truly be a masterful Chloro.
Withering Vines
Withering Vines creates an AoE heal for more than Vile Spores - but only heals targets within 7 metres of the mob you cast it on. You get the Withering Vines HoT and also a Lifegiving Veil heal from the first tick of the DoT.
Vile Spores creates a much wider radius AoE heal, for less than Withering Vines... and also heals the Synthesised Tank for far more than Withering Vines.
All in all...
- If you need to maintain high level of healing on the synthesised tank, then you should always use Vile Spores in preference to Withering Vines.
- If you need to AoE heal group/raid members further away from the mob, then you should always use Vile Spores in preference to Withering Vines.
- If there are several melee group/raid members taking damage from a mob - and you don't need to worry about the synthesised tank. Then Withering Vines will be a better heal.
Balancing toward DPS for Group Contribution
If you are healing extremely comfortably, you may want to improve your contribution to the group, by increasing your DPS. You can do this by choosing to use Stream of Reclamation more. Stream of Reclamation is a channeled spell but doesn't use up charge. It delivers a great deal of damage and the first tick will give a 90% Lifegiving Veil heal. At the same time, each tick increases the proc chance of Radiant Spores on that target. Nevertheless, you could cast 3 other healing spells in the time it takes to channel Stream of Reclamation... so you will lose some healing overall when using it.
So you gain a lot of extra damage but lose some of your healing. Use Stream of Reclamation only when you're healing the group very easily and can be confident that the healing you lose by using it, won't cause problems for keeping the team alive.
Also, if you're healing very comfortably, then you may want to stagger your usage of Nature's Corrosion enhanced Vile Spores a little more. Nature's Corrosion adds a 6 second DoT to the end of Vile Spores (and Ruin) which does 100% of the damage done by the nuke. The Vile Spores DoT will be over-written if you cast Vile Spores again. You'll always get the extra heal from the first tick... but you may not get the 2nd and 3rd ticks of the DoT. So some people like to try to leave the next Vile Spores as long as possible, so that you get more ticks of the Vile Spores DoT. This is quite advanced though... and you should make sure that you don't let your healing drop too much, just because you're waiting for a bit of DPS. Your prime goal is to heal - not to DPS.
You can go for Chloro as a minimal secondary soul in several ways - all of these are predicated on you having a DPS main soul from which most of your casting will come. These mix in Chloro casting to varying degrees, based on how much healing you want and the type of healing you'd want.
1. The Basic Secondary Healer.
This is for Radiant Spores on the group's focus target, enhanced by using Stream of Reclamation. Use Withering Vines as a DoT with a bit of extra healing. You don't cast Vile Spores.
This will be enough Life casting to keep up the intelligence buff. You also get Entropic Veil which is a very early damage increaser which can be useful with some souls that don't get one or only get it later. Obviously, you also get the instacast bloom as a spot heal.
2. The Basic Lifegiving Veil Healer.
Extends the Basic Secondary Healer to include more Lifegiving Veil healing. You have the same basic approach to rotations and get a little extra healing from your WV and SoR from the first tick healing through Lifegiving Veil... but have the option of mixing in more Vile Spores primarily for tank healing through Synthesis.
You're basically still just doing the passive more DPS focussed stuff - but when the tank takes spikes or the group gets hits with an AoE, you mix in some Vile Spores to provide some back up 'spot healing' to help the main healer cope with the situatiion.
3. The Basic Rift/Invasion Support Healer.
This one doesn't use Synthesis. You'll often find that in Rift/Invasion situations, there isn't a clear tank that you want to heal. This build does take Phytogenesis to get the AoE and improved proc chance Radiant Spores. You also get Improved Ruin/Vile Spores which increases your DPS with those spells and improves the AoE healing from them by 30%.
Again, you mix in the Vile Spores and Ruin as needed. If the raid isn't taking much damage and AoE Radiant Spores is largely covering things, then you lean more toward your Main Soul's DPS. When you want to add more healing to the mix, you throw in your Vile Spores and Ruin - and with the added damage from Nature's Corrosion, you don't sacrifice too much DPS to do so.
4. The Basic Instance Healer.
At higher levels, with this many points in a secondary soul, and with the a fair bit of support from a Bard or a low healing specced Cleric, you can main heal an instance with this kind of set-up if you need to. It probably also needs to be a good tank for you to heal high level content with this set-up. This is also the basic 16 point set-up that you would use if you were level 16 and wanting to heal your first instance as a main healer... so the basic tool-set is all there.... and the rotation and spell choice advice from the Basic Guide in the OP would apply.
But you can use this set-up as a secondary healing set-up too. Similar approach as for the Basic Lifegiving Veil Healer. You put up Radiant Spores, throw in the odd Withering Vines and/or Stream of Reclamation. For support healing you go first to Bloom and Flourish - as they are reactive and instant and will disturb your DPS casting less. Remember, you're support healing, so your priorities change. Focus on DPS spells from your main soul.
Only when you feel you need to support the heals of the main healer, do you switch to Nature's Touch, Ruin and if necessary Vile Spores. Use Ruin as a reactive AoE heal to help out the group. Use Nature's Touch as a Tank heal and only go to Vile Spores when the main healer is just totally struggling.
If you want to focus a little more on the NT/Ruin/VS healing, then you might also take Nature's Corrosion to add to this build still further at higher end.