don't worry - you're well within blizzard's ToS.

My main dungeon team is a pally, priest, 3xmage. I started with my priest as holy, and eventually switched to disc and it made a big difference in keeping my team up. Priests have a lot of utility and decent buffs. Tough call ... the shaman can't heal the group as well as a priest can, but offers really good single target healing. I may consider going with the shaman only because you get good buffs for the rest of your group from the totems (spell power, resistances, armor boost, passive healing, mana regen etc.). It's pretty close though IMO