While I would agree that healer is a specific mindset, and I say that from having played the class in multiple MMOs, what others have said above is also true. There are many factors that can contribute to the success of dungeons, especially when perhaps the dungeon level doesn't allow you to use all the skills on your bar if you're significantly over level. Over enthusiastic tanks pulling too many mobs and not being able to maintain aggro. Tanks that position poorly and DPS that pull aggro off the tank. Poorly geared DPS that become highly squishy to AOEs can also end up burning a lot of your manna. The trick is to try and stay one step ahead of the damage while not wasting MP on unneccesary heals. Use MP potions and MP regen skills early in these cases so you may get the chance of another pop towards the end. If a group is particularly sticky don't sweat trying to do much DPS. An extra 5 minutes in a dungeon beats wiping and restarting any day of the week. Also, remember, it's just a game.