I'm gonna go out on a limb and say it was him. Why? Unless the DPS is so low that it takes way too long to kill things, with the healer's gear properly gemmed, enchanted, and reforged he should be fine without drinking for an entire heroic. The other clue is that he said your damage intake was fine.
Originally Posted by BryceE
My 2c, I don't pretend to know if DK's should stack mastery at the cost of all else, someone else will have to add that in.
EDIT: You have 5 pieces of unenchanted gear, I would start there. I understand your shoulders are less than crappy, but luckily shoulders and head are the cheapest.
"There are no men like me...only me."