Personally i find arcance nexus the strongest global. Every turn this spell is in game it gives the caster more gems to recast a stronger version in future.
I always got stomach pain
if someone cast this one and it needs an immediate counter action.
LA ermor is very special, try it out in the next game ironhawk
. Maybe you'll change your mind after losing some big undead armies to counterforces which you didn't really hurt.