When I did my first playthrough with my warlock, I had some problems with them, because I wasn't used to the mechanics yet, since I never played a Divinity game. But now, it's really OK. Like with most fights, you have to think a bit and use your environment (I didn't realize, how important high ground was at first), but it's doable.
Sneaking to the side and using the hight advantage against them really helps a lot.
