hey man Medìk here, i have the same setup you do except for resto druid we have a shammy, and i also heal a hunter/mage kiting combo during P1, i feel i can shed some advice and knowledge your way to help out as we just downed nef this past week for our first time.
P1 healing: I start off the encounter throwing lightwell in the center of the room, then jumping into Chakra Serenity. i like to keep a rolling renew up on the hunter via Heal spam in Serenity as well as having the HW: Serenity to heal incoming spike damage to the hunter. One thing your NEED to be doing if you aren't already is properly switching to Inner Will ANYTIME you perform ANY instant cast to concerve mana if your having mana issues. and of course properly switching back to Inner Fire when casting heals. that said, what i like to do is keep PWS on the hunter on Weakened Soul's CD to help mitigate spikes in damage but more importantly to grant him Body and Soul to help him kite to avoid damage, i like to keep PWS on the mage when he goes in to Nova as if he's to close after a nova he will take some serious spike damage as well, just keep PoM on the hunter PWS on cd and keep spamming heal and HW:Serenity on him to keep him up this is very mana efficient and should keep them alive long enough until adds die. as for electrocute healing i've been experimenting as i have Dark Intent on myself with renew healing along with Lightwell and after Electrocutes i've been renewing the entire raid while in Inner Will of course and having them click lightwell along with CoH. (again this may not be the smartest way i've been experimenting along with Dark intent) we also have a shaman immediately after the first electrocute drop mana tide... although much of it gets wasted as we spike back to 100% mana quickly from it we do this to get 3 mana tides into the encounter. for you i would reccommend having the raid properly distributed so that you can POH the raid back up along with CoH and everyone should be using up lightwell during electrocutes. without mana tide this should leave you entering Phase 2 with somewhere around 75 - 80% mana.
P2 healing: this is where i think you will find the most usefull information. in P2 believe it or not i actually regen A LOT of mana healing with this technique. what i do is stay in Chakra Serenity, hop into Inner Will throw PoM first then renew on everyone on my pillar, jump back to Inner Fire and continue to spam Heal to keep renews rolling, using HW:Serenity on CD and SoL Proccs along with jumping back into Inner Will to recast PoM when the 5th PoM jump is used up, (important not to recast PoM on CD but rather when the 5th PoM is used up) healing with this meathod during phase to allows me to actually regen mana and i do NOT use lightwell on my pillar, you want to throw it down immediately when you jump off of the pillars near where your group is tanking him to help with healing after electrocutes. It's important to note that we do not push ANY electrocutes during P2 and Interrupters HAVE to not let ANY blast nova's off and you will be able to regen mana or stay steady at mana with this method given the amount of spirit that you have.
edit: i also recommend what above posters have stated about re arranging it so that you only heal 3 members total on your platform that is what i do when i heal with this method. hope everything helps