I would also add the fact - tha the most powerfull artefacts are weapons - with the correct woman (hell girl) you can have 4 weapons - that makes warrior valuable even if nothing else would.
It needs only little luck and you would have collection of the best weapon artefacts - by this you can make from you warrior excellent mage (using the +5 to INT weapon/staffs) or total slayer (I had 2 swords of +50% DMG to dragons when I was in the labyrinth, or 3 + x% against demons when I was fighting demons - I am not sure if it was 50% or 30% ...)
I would never believe that this can make a difference myself - but I never had such easy fights on impossible than when combining the best of the best weapon artifacts
btw - I totally liked most the palladin - but not on impossible
why is mage not so great on impossible? - his magic increases in power linear (in linear matter- you have twice INT your spells do twice DMG, but you can get much more DMG in impossible combat than you could ever fix with ressurection)
as the difficulty increases geometrically, you lose in time...