Does MgS cut GA damage as well? (in General)

Simple Question which I think requires nothing more then a simple answer.

As far as I know the MgS only can reduce DD spells.

Per the spell description page:

GA retaliates with a percentage of all damage inflicted on its targets by opposing Minions. GA damage is reduced by AC; GA damage type is the same as that for which GA is retaliating.

So if the damage was from a DD spell, yes the MgS should in theory protect from the DD spell.

HOWEVER, this is the problem. Someone who wears a MgS cannot cast a DD spell with the exception of perhaps a base decay spell (?loophole). As we all know the MgS makes all spells and enchantments have a level of zero.

I see, so on top of the fact that you get to use decay with a Mage Shield, you also get to block the GA damage from it. But if I hit you with physical damage while holding a Mage Shield, which I assume is the only damage your suppose to do with it, then you get no GA protection. That sounds like a bigger loophole then I thought it was. Thanks Ranger.