What should I infuse my blm with?

[Dyvid]

Well don't do Piety anyway, because from 4.0 it's a healer only secondary stat. Because tanks, dps and healers will all have a secondary stat unique to their role you probably won't even be able to meld it.

From what the maths people have been figuring out with regards to rotations, it's unfortunate since on a normal rotation you'll have to be at 100% MP when you cast Fire 3 in order to get 6 F4 in per rotation, which may mean waiting on mana ticks, or even just sticking with 5 F4 instead.

I would say ACC might be a useful meld but it's hard to say until we see 4.0 patch notes.