Originally Posted by
Starmind
Always, and I mean ALWAYS, choose paladin if you don't already have a paladin in your setup.
Holy priest lacks any sort of utility or damage reductions for your raid, and your healing cooldown (divine hymn) remains the weakest cooldown in the raid. What you can provide as a holy priest is a competitive output, but that really is not enough.
As a disc priest you get a harder-to-play class but with pretty good utility. Your output will suffer, however.
But like I said, if you don't have a paladin in your lineup: play one! The spot that a holy priest might compete with would be druid or monk, but as we all know, there's nothing a holy priest can do that a druid can't do much better.