Warrior, Mage, or Paladin?

Choosing a hero class based on a unique ability that you'll get at some unspecified level isn't very rational. It's much more important to consider the distribution of runes you receive, as well as skill growth.
In this regard, the Paladin has one significant advantage: his Spirit runes are in demand for almost all skills.

Added 1 minute ago


However, Resurrection is placed in the spellbook at the start. Considering how difficult it is to find this spell, it's a good bonus.

Yes, Spirit runes are needed very often. Although, most of them are in the Paladin branch. Another question is that the most useful inter-class skills are in this branch :(.

But I disagree with the idea that choosing a class based on abilities is irrational. For the Mage, both "Higher Magic" and "Alchemy" significantly enhance their main weapon - magic. The Warrior has a super useful Rage ability (I've forgotten what the ability at the very bottom of the list is). And in PvD, I got "Higher Magic" at level 5 (although I was playing on easy :o). I think that getting the lower-level ability of one of the branches is possible around level 10-11 :).