I am loving the new hero types.  They could probably still use some tweaking, but the concepts are very solid.  However, we could still use a few more heroic types.  I mean, seriously, where are the spell casters?
I'm not sure if Piranha and Snotling have some big 'magic system' update planned.  But, if they don't, here are a few hero types that would add a splash of magic to the game.
Priest,Priestess or Cleric>  There was some discussion around a healing mechanic on a thread I started.  Although I proposed one mechanic, I actually preferred the one KGB suggested.  Healing would be a chance for a unit to regain a hp after defeating an enemy unit in battle.  A Priest type would give a % chance to heal to his stack.  Group warding would also fit a cleric quite well.
Sorcerer, Warlock, Mage>  DLR had a mechanic called 'lightning'.  Lightning worked a bit like ambush, except that, instead of killing outright, it would halve the enemy unit's remaining hp (it would kill units with 1 hp though).  Just like ambush but weaker?  What is the point of that?  Well, the other difference is that a unit with lightning would get a chance to blast each unit it faced in combat.  Ambush only works once.  Warding would be an effective defense against lightning.
Another interesting power for a mage would be 'magic portal'.  With this power you could vector units directly to that hero.  Buying additional levels in this power would decrease the transit time.