I might be missing something crucial here as usual but wouldn't Glyph of Shadow Word: Pain be kind of attractive
for disc/holy just making sure to keep SW:P up?
you would miss out on a vital glyph otherwise, running oom as a healer isn't a huge problem, I can see it in pvp maybe.
The glyph to a non shadow priest is worth 64.3 mp5, shadow word pain is 764 mana and lasts 6 ticks.
Do the math...
'u get constant hit by ice shit from roof so you can travel instantly all across the room'