It would be partially that you're probably not completely familiar with the holy style and spell usage / keybinds etc etc after being disc for a long time. I doubt your gear would impact it that much. Going from what I've seen with 5mans so far, and what I know from MoP CM's i'd say that there's a LOT of tank damage, which disc would manage a lot better than holy. Until I do some myself though I can't really say anything with certainty.