It doesn't feel too unique, but it is really fun.
I don't really imagine them healing by dealing damage, but if it's fun I could get behind it.
For fantasy, they are missing battle-resurrection, as their WC3 "Resurrection" ultimate revived 6 nearby corpses.
If they ever got an ability that perhaps temporarily revived multiple targets (perhaps as 'holy warriors' like the old DK Raise Ally used to make player ghouls, so abilities couldn't be abused in combo with it) that would be good.