I think many already know how to do this bug, but many people do not know, i only learned this same bug on level 60. Then I'll do a little tutorial here.
1. Press and hold R, now click several times on target, you'll atk your target very fast. [i recommend this bug for only PVE because you need to point your mouse on target,]
Now the same bug but different, better for PVP.
2. Press and hold R, click several times with the right button at your "Attack" in your skills bar. Like this image. [if your target will run you hit it anyway]
Many people use the bug W1W1W1 ... but I prefer these, come here and share with you guys.
I hope you enjoy it.
[Sorry for my english]