This guild is very similar to where we are in game.
Our guild is farming Tacvi and Anguish - we actually broke into Anguish the week before we got into Tacvi. So compared to the other guilds on our server who have downed Vish we are undergeared. Most of the guild only has 1 or 2 pieces from Anguish. Most of my heal team is under 10k mana unbuffed - I think 3 of the ones on for the win tonight are over 10k unbuffed.
Anyway, we had 8 clerics and 2 druids - 4 or 5 pallies and 2 shaman. Clerics were on a CH rot - tight, no pause - skipping to do group heals when needed (pretty much 1 of the 8 skipped each round so we didn't have more than 1 skipping in any given round of the rotation). Druids, Shaman and Pallies were healing as well. Mana checks every time a Cloud popped and if anyone was below 50% we went ahead and killed a cloud - the last cloud died maybe 1 minute before Vish so we did pretty good on mana.
My notes:
Make sure everyone has DA and DB loaded as well as bestow DA if they have it - so it can be put on the MA (as above, and remember Bards have a bestow DA as well so get them to help out). Audio Triggers ROCK for this event so you don't have to watch the buff window (since the icon is the same as the AE) and if a cleric can't get to a cure NPC they just DA or DB themselves when there is about 10 seconds left on the DT. Have all the casters bind right outside, and have Wizzy's do AE TL at 27% of Vish's health then refresh when it poofs. If casters can't get a cure take the TL. Clerics can take the TL and die in BL from the DT then loot their corpse and use DR on themselves and come back in at full mana. The big thing is not to die in the instance because it just makes more adds.