I think they should have more defensive abilities that rival what the Juggernauts can do offensively.
A few things off of the top of my head are:
1. innate -50% damage from physical attacks/
2. +1 defense every time they are attacked/
3. weapon break= unit absorbs next attack and the unit that attacked them have 50% less attack for remainder of battle/
4. spell absorption= if a spell is cast on them before their next turn they can absorb the damage from the spell and get 1 random buff dependent on the nature of spell that was cast. this buff should be permanent for that unit until death or dispelled/
Anyway, these guys should be a pain to kill.
