I agree about the disadvantages of the warrior build. What worked for me was a mage/ranger, with some priestly skills like Summon Demo and Hide in Shadows. With a good mage/ranger build you can do excellent ranged damage using both Fireball and Exploding Arrows. One of the great things about Divinity DKS is the way your character can roll, dodge, do backflips, etc, which works really well with a primarily ranged fighter. I tired melee fighting but all too often got overwhelmed by numbers, but a good ranged fighter can take out a lot of tough bad guys without anyone getting near him/her.
I said in another post that a good boss battle should be a sort of final exam on what youv'e learned in the game and that was true with Berlihn and Ygerna on hard difficulty. Ygerna has a very strong rush attack but I was able to dodge it and keep her at a distance while I pelted her with ranged attacks, occasionally using Hide in Shadows to heal, change position, etc.So I think that in this game a little flexibility goes a long way.
