As a healer, I have only run out of mana once or twice in Expert Roulette. It was because both the tank and DPS were under-geared and not using skills properly. For example the DRK didn't have Grit on....
This caused not only long drawn out fights but also the necessity to heal the tank instead of being able to DPS.
I use my MP regen skills as much as possible. Even going into a boss fight at less than 50% MP is no problem in Expert Roulettes, unless the other members don't know what they are doing or under-geared.
Just in case, I carry an ample supply of MP pots.
(Although I really do hate going into the final boss fight in The Vault without full MP. Not Expert Roulette though.)
The only time I have a problem with the tank pulling tons of mobs is when either:
A.) They can't hold hate and everything comes after the DPS or me.
B.) They die faster than I can cure, even with increased spell speed.
If I am doing absolutely no DPS and using everything I have to heal the tank and they still die, then it's time to change the strategy. MP is very rarely an issue.
If I am spamming holy and things are still not dead, I will notice my MP getting dangerously low. I'll stop using Holy and switch to something else.
