Why are there none in wz and the one left know there limits and never open on anyone but a wounded animal.
Um, that's how you're supposed to play a stealth class...
Only an idiot opens up right in the middle of a huge battle. You're basically begging for death if you do that. Smart players wait for the opportune moment, waiting for someone to stray away or taking out a low health target and quickly vanishing again.
If you're wanting stealth classes to be able to pop out whenever and own the entire battlefield you're basically asking for the class to be made OP.