Even in that ideal situation, the buffs in your list require 10 different people (including 4 clerics) to sustain 166/tick regen (I didn't think about mod rods and didn't count yaulp, a 4 second rotation is stretching it on any relevant content to a bard with maxed singing mods and a guild full of clerics like that). You can't use a horse to kill the avatar of war, but that content is 2 expansions old. You could 12 man it anyways with normal mana regen and command of druzzil
You're still better off using your bards for other things than cleric's mana in almost every situation.