I think the good old Demona is still the best Warlock respawn...
There is also warlock at Inquisition, in "The Arcanum", but I do not recommend it... because there are many other creatures with it.. Diabolic Imps, Lichs, Djinns, Demons, Undead Dragons... Making it extremely annoying to hunt there!
Plus, in Demona there are many corners in which you can trap the Warlocks. In the Arcanum the rooms are circular, so there is no good corner, they will run away. Thats why I recommend Demona!