you're too low on haste... get 7,5% unbuffed (since I assume you're raiding with a boomkin or shadow priest for the 5% bonus) renew gets an extra tick at 12,5% thats what we should aim for other than that mastery would help...
Using Inner Will instead of Inner Fire helps to cast more Renews, CoHs and PoMs, even if they heal for less (since IF gives SP) you can use them more, using renew as a filler spell usually it's better than FH - assuming people aren't on danger of dieing, if they're throw them a FH ofc
I'm raiding 10 man only but still renew represents most of my healing, however if you feel confortable about your mana regen you could still use Inner Fire and spam all those Instant Cast Spells
And like has been said before in this thread since you're running 25 man going full time Sanctuary Chackra is almost mandatory (unless for Chimaeron where serenity just feels OP, remember to switch back to Sanctuary for Feud phase)