When Cata was out on December 7th , I kept hearing that Disc is rubbish now and broken.
Ofc I immediately disagreed and was counting on the fact that blizzard knows what they are doing.... Usually.

So I'm glad to say.... Disc aint rubbish, Disc is far from being rubbish.
Disc is not intended for tank-only healing and can easily perform well on raid healing.

You just need to put the Wrath-shieldspam-whack-a-mole-flashheal-mentality in a box , close it, and throw the key away.

Here is a fresh lovely article from 28th December about the state of disc.

http://talesofapriest.com/2010/12/28/the-cataclysmic-state-of-disc/

Enjoy !