While I am equally befuddled by the OP's apparent complete lack of respect for Lustrate as an "oh shit" ability, some of the discussion did give me a funny idea for a totally reasonable 3-5 minute cooldown for SCH that would not make us really that much more powerful, but still be a satisfying pre-"oh shit" button.

Xanatos Gambit (named for fun)
Cooldown: 5min
Effect:
Guarantees a critical on the next healing spell.


I'll grant, it steps on MNK's toes a bit. The cooldown is too long to be used in a normal healing situation, but can guarantee a double shield before that nasty Mountain Buster.