Toxic Tolerance

It seems that you only get splashed if you are HITTING the revasaurs. Best thing to do is to unequip your weapon and beat on em with your fists while AFK

If you're like me and you're lvl 80, you might have a problem with, "Oh CRAP, i keep killing them in 3 or 4 hits even when i'm unarmed!" I found the best thing to do if you're lvl 80 (or in the 70s) is to take off all your gear and the attack the mobs, you shouldn't do very much damage and you should be able to get the 20 splashes really quickly. If that doesn't work, you can also try letting them kill you and getting res sickness.

To all the other level 100's and future 110's...

Get the Goblin Dragon Gun, Mark II from the AH (generally about 500g), and use that as this has worked for me as of 6.2.4.

Tip: Since it does damage in a cone, it will be better if you can group multiple venomhides near each other to maximise your potential for getting the credit. Hope this helps! :)