I see you haven't discovered some of the new old spells, like Ice Orb or Soul Draining, hehe. As for glot's armor, it's a part of one of the best combos of KBTL: skelly archers + dragon arrows + glot's armor = death to black dragons

I'll have to try it out in KBCW, I have no archers yet. They may be not so good now, with low leadership of mage hero.
School of Piranha (or Evil Shoal) was one of the best rage skills in the early game in KBTL. It's still good, but I think that you can easily get it too late. But it's very strong, it's total damage heavier than most spells. It can be tricky to position, but I have perfected it in KBTL, so is no problem now.
One of the least impressing rage-skill-turned-spell is Poisonous Spit, I think. But it's distortion school, so may be useful if you maxed distortion and not chaos.
Gizmo is not really useful, it would be if it wasn't spell but rage skill, tough. It's too situational and unpredictable (it randomly heal or attacks). In KBTL I used it mostly to level rage spirit up.
Ice thorns are great for keeping last non-ranged survivors in bay and resurrecting, but I'd prefer it to be cheaper.
Stone Rain... I have yet to find it. It was quite nice in KBTL but only after upgrading (area was huge), but I don't know how it upgrades now.
Dragon of Chaos is completely new spell, not taken from KBTL, and I haven't found it.