Do we have any way of establishing the level 85 MP5 formula at this point?
It seems that whatever the formula is, it's no longer based on the old:
ManaRegen = (0.001+(Spirit * BASE_REGEN[LEVEL] * (Intelligence^0.5))*5
As solving that equation for BASE_REGEN[85] gives different values depending on the stat set in question, which really should not be happening given it's suppoed to be a constant.
Based on quick testing so far it seems that both Spi and Int are contributing (although Int to a far, far lesser degree) and that at the simplest, roughest level it seems that Spirit on gear turns into between 91-98% OOC MP5.
It seems there might also be a DR on it to throw another spanner in the works, which may make sense given that Spirit is being treated as a rating rather than a stat for the purposes of reforging.