Talking to people about this before, we knew AST sheilds would get increased, when what they really need is a lower cast time to match SCH. (They were already higher than SCH)
But we talked about the changes to buffs duration, and the CD of draw.
(pretty much what happened, but stronger)

But the idea was that it was only locked to one set, so they only get longer buffs, if they are Off Healing, and not main healing.
(Which, based on WHM complaints already, would make for a great balance)

So here is my 2 cents on making the change only apply to their sheild stance, which i forget which that one is called atm.