RR9L1 Eld here.
Power management is real in RvR since you want to maximize your RAs for more utility or dmg.
After testing several mana reg RA setups I ended up with the bare essentials of MCL 1 and Serenity 1. Especially with pots Tasy Chunk of Legion to restore your mana in a pinch, this is really all you need.
However, keep in mind that you MUST absolutely maximize all your toys to gain power. Chug a pot the second it's getting you back to full power, use MCL wisely when you can find the space during a fight. Only use the mana charge as a last resort but don't hesitate to use it if needed. The key is to get used to pot-mcl-charge-power management.
You definitely need MCL 1 at least since it will help you get minimal power right after getting rezzed. You can save the pot or charge to get extra HP if you get PR'd. Serenity 1 is just one point. I've noticed a difference and I find it worthwhile for sure.
For a healing class I would definitely consider MCL2. I don't think serenity 2 is worth it for them.
PS: I only use blue potted pom.