So basically from what I can understand, in order to make Benison not useless, you want Benison to effectively have no cooldown, retain it's instant cast and 0 MP cost, and shields HP to the point where it will not break for the whole 15 seconds (effectively a 15 second Hallowed Ground)? Lol
If WHM gets that I want a real Bahamut summon. One shots the entire raid and makes me roll 99 on every piece of loot I want. Bwah ha ha ha ha!