My experiences have shown that they are available - the problem is that they become available around lvl 35-40 (maybe sooner if you manage to luck out with geyser or death star in good locations - for example, I found mine in montero once and in verona twice), which is pretty late in the game, and till then, as you put it, "tank'n'spank" is the usual way, I agree.
Temjin made an intresting suggestion. Well, evlin is a spell that kills part of a living stack, but it does require a corpse, which is kind of hard to find in the beginning of the battle
However, I still feel that there may be a way to do a playthrough where the spell damage will be the dominant one. All I need is a lot of mana, a stack of Black Knights and some spells. Might be fun to try it out.