Once I get the game, I'll try focusing on the "Withering Flame," "Fire Wrath," and "Scorched Earth" skills. Also, there's a new interesting ability in logistics called WarPath, but then you'll have to choose between it and Urgash's Call if you aim to upgrade that one...
A pleasant exception is the demon ballista – it's all good, both the rapid-fire ballista and the fire arrows... (it's just a pity there are no rune machines :D although in the new game, that wouldn't seem unusual).