Using my current gear, in WoWHead profiler, switching talent specs and changing all yellow gems to SP+Int, plus a few of the Blue gems to SP+Int as well, keeping 1 blue SP+MP5 to keep my meta active, puts my (according to WoWHead profiler) at roughly 28.5k mana unbuffed, and ~3400 sp unbuffed, 22% haste unbuffed and 25% crit (without the holy crit +% from talent). This seems decent to me, not perfect, but decent, switching back to holy spec with that same gear, everything seems decent except the haste is a bit low, but I'd be staying Disc primarily, with Holy only really when/if needed.
Another question, about how Borrowed Time works exactly. If I cast PW:S, Borrowed Time procs, giving me 25% haste for my next spell, that doesn't apply to my actual haste number correct? Meaning it won't decrease my next GCD by whatever (albeit small) % that would decrease the GCD as if I had that much more haste, since I am not even close to the haste-GCD cap, it only would really apply to a casted heal, i.e. Greater Heal, Penance, Flash Heal, PoH?
WoWHead Profile - Current Gear - Gems Swapped -- I swapped out my current t9 shoulders for the 251 t10 shoulders, since I'm < 10 badges from them.