So far even with an 80k mana pool it only takes one mob to drain it completely, and this isn't just myself. So far every healer on the realm with the exception of shamans are having problems maintaining their mana pools even with pro groups that do everything right. I think that the raid mechanics are fun and all, but I think they should just go ahead and put those mechanics back in raids, OR fix the dungeon finder tool to provide at least two viable CC'ers since it's required in these new dungeons on their heroic modes.
I know it didn't matter what kind of group you had in WoTLK so the dungeon tool could be non-discriminate and pick up whatever classes were available..., but with the requirements of cataclysm heroic dungeons, if the groups are not tailored to what is needed the pugs will always be fail no matter how good the individual players are in them.
Ok. As a tank, I see this often, as often as I don't see it. Healers going OOM left and right. Just like I see DPS or other tanks standing in fire / damage / not avoiding crap. Healers are spamming out their biggest spells....and on and on and on.
The fault is really the healers pretty often (yes, really). You need to let the DPS die. You NEED to. For the sake of your mana. Bad dps are bad, if they take excessive dmg constantly, it's their fault. If the tank is being bad and stupid and not using CC when it's available and takes massive damage from not moving...then you need another tank, or he needs some strong "advice".
Our healer in heroics is a priest and keeps down a Lightwell for DPS, and only heals them if they need it (boss effects and unavoidable burst dmg). She goes OOM maybe 20% of the time. In heroics. In regulars I see healers going OOM every single pull. They spam the fast spells, that consume massive mana, left and right.
There is a lot of L2P to spread around, and I've grouped with a few spectacular healers (in pugs no less) that have never gone oom. It's amazing, even without CC they don't. I think healers need to play as healers and try things out, and stop pretending they can level as DPS and heal with no cata heal experience.