The Tale of Flame Dart and Sunder.
Played a game with a dedicated spellcaster: a custom Magnar Warlock Fire Disciple with all the casting related starting skills and equipment.
Stole Spirit from my first champ (Air Apprentice) and off I went...
Flame Dart and Sunder were my main damage skills. Starting from around level 5 or so I was able to one shot just about any target: flame dart killed fleshies, sunder killed elementals (and most guys immune to fire happen to be elementals/demons i.e. extremely vulnerable to sunder). By the time the game was over, my Sunder damage was listed in tactical combat at around 300, while Flame Dart clocked in at about half as much. What's my point? I guess the point is that with a very specialized build magic can be downright overwhelming. I don't think it's a balance issue, as the AI will never be able to successfully specialize like that, but boy do those Warlock/Path of Mage/Ceresa's Staff/Evoker synergies work like a charm. I mean heck, at the end of the game even fire resistant units died to flame dart.
Anyway, so much for my experience with the mage guy. Now if you excuse me, I'm gonna go build a magic-immune Ironeer sovereign and bash my way to victory without ever casting a tactical spell.
rvgr