Why not add to the aura of death a bit of aerial damage? like 2-3 every turn, this will work nicely with Poison Cloud.
For Warrior, or any other melee class I'm missing an ability to survive critical strikes. for now, if you are constrained by a golem or snake and you don't have any escape mechanism, you are dead. Having a shield block for 1 turn will not really save you.
I also really liked having weapon mastery on Duelist. I think without that, it's a bit harder to play, especially taking into account that to have a proper build, you need to have at least 14 in Dex. And if you are unlucky with attributes gain, your melee dmg will be very low and it will be more profitable to play as a ranged class, which does not really scale with his skills (except strafe attack).
Killing Strikes - I tried to play with that, but the benefit is not obvious. If your enemy has to be lower than 20-30% at the moment when you attack, this is really rare if you have good damage. For example, if you have 20+dmg, your enemy should have 100+ hp and there are not that many creatures like that. So after a few tries I never level up those. But maybe I don't understand how that works.
The game is great!
Regards,
Andrew.