I dislike the idea of nerfing magic, especially as it's currently implemented. I would, however, like to see a bit more incremental scaling (magic damage racking up incrementally, traits that improve buff/debuff performance by +X per rank, etc).
Personally, I'd prefer a tactical spell that dispels all enchantments on a unit (or 2 spells, one for positive and one for negative spells) that's unlocked via Sorcery or another midgame tech, so all champions can cast it. If that's not possible for whatever reason, then a turn limit would be an acceptable alternative.