As a rule, sufficient skills and education are enough to create a quite strong hero.
Education is a good thing! But you have to sacrifice something... Do you think it should be summoning?
But then the opponent can increase their luck and gain magic resistance, and there are quite a few such artifacts. Chaos will be semi-useless, and that's it.
I think a Warlock simply needs two schools of magic.
And there isn't enough space for education, so I take Healer.