I use power crystals on my sorc, main and offhand. Full on expertise is probably overkill. (Not sure if you mean you don't use power crystals or just don't need a white one, if the latter is true then disregard).
It's pretty much a break even scenario from 1300 on forward - you don't actually lose/gain anything from them from a damage inc/outgoing standpoint.
However, stacking expertise into the mid 1300's still provides minor benefits to healing (which is what I do).
I run at 1320 expertise these days, I have one advance resolve 27 armoring (non expertise) I use that drops 50 off of my max already.