Here is a quote from a Blizzard poster concerning a hotfix that went out today:

We are making a hotfix (any minute now probably) so that Replenishment in arenas will only affect the character and not the whole team. It will continue to function as it does currently outside of arenas.

We feel Replenishment is balanced for larger groups, but just makes too much of a difference on smaller arena teams. Making the rules work differently in PvP and PvE isn’t a solution we like to use often, but in this case we think it fixes the issue cleanly, while still making the talents in question useful to the character who takes them. Alternatives, such as nerfing the amount returned by Replenishment in arena or making it not function at all, seem like more punitive choices from which we want to stay away. (source)

Well that's pretty neat. I will have to say that Ret+healer and survival+healer HAS been giving us some trouble in these early-goings of the six arena season. Largely, I believe it is because of the mana longevity AND damage output of each class, but I definitely have to say that Replenishment not working in the arenas will balance those two comps closer to a manageable level for us. We played a fairly decent Hunter+Pally team, and the only reason we lost was due to the fact that the paladin had infinite mana from Replenishment and Divine Plea, and it's just not prudent to dispel Replenishment off (not even sure if one CAN dispel it off... DP sure... NEED to dispel that). Anyway, Survival+Healer should be a little more manageable now as their damage is strong, but manageable and their mana drain isn't an instant game-winner. Ret pallies do a LOT of damage, but it is very manageable if there's a healer, and we can usually turtle a lot of the ret pally's damage and mana burn every cycle of cds and apply some pressure from cat.