I'd only worry about damage shields personally. ${Target.DSed.ID} > 0
I'd check against the target being named and red con, coz many have 'permanent' beneficial buffs that can't be stripped.
I'd also prefer to have a robe caster, cast eradicate magic, if possible, rather than using up an 8 second cast time on skull of null.
I'd also prefer to get Kijarl's Ring of Negation from PoWar, coz it has a shorter cast and cooldown timer. Even better have a monk with his Anguish BP cast 'silent disturbance' instead.