I love how heaps of the arguements in this thread are "LOLOLOL SHIELD SPAM IS FUN LOL".
Holy isn't any different these days, you change shield spam to renew, and you still use the same 3 spells (disc has 4).
Renew/Shield
PoM
Flash Heal
and Penance for Disc.
And for the record, my priest is Disc specced currently with Holy as my off spec, and i have healed all IC bosses other then LK as both Disc and Holy.