I have messed around with a druid healer on MoP and think that it is probably the best suited to lock healing. Locks are fairly resilient to start with so the dot style of healing works quite nicely with lifebloom for any focussed toon. Druids are getting some really nice defensive tricks back again as well as the ability to switch stacks of lifeblooms to compensate for lack of burst healing when targets are switched. On top of this, the druid currently gives one lock the ability to cast rejuv which will allow for some greater healing flexibility...

I am liking the look of locks in MoP also, esp. demo. The ability to switch into a tank form and stay there permanently if required whilst still doing some reasonable dps is nice. On top of that, if you have the improved imp, you get one of the best defensive dispel mechanics in the game... aoe (up to 5 targets) dispel every 10 seconds. The tooltip even mentions it can remove stuns although I have not actually tested it yet.