Yeah, like I said LW is definitely an appealing option because of the Draconic Embossment but I don't think healers are going to be able to prioritize throughput early in the expansion. Mana was in such short supply on the beta that hardcore healers are going to have to consider not going OOM as part of their min/maxing. It's possible that in later tiers mana problems will disappear again (just as they did in Wrath) and LW will become appealing, but that will depend on how Blizzard scales our characters and the fight tuning in each successive tier.

The math I did this week isn't complete, so I'll need to get back to you. I did some preliminary glance overs comparing the proc and use effects of tailoring and engi versus passive bonuses from LW and other professions. At first glance nothing can touch tailoring for mana, and engi is the next best thing. I'd cherry pick those two for mana right now if I could. If a healer is able to manage the procs from tailoring while using the cooldowns from engineering she or he should be well ahead everyone else. Being able to time the use of Synapse springs with the natural breaks and lulls in the fight is extremely underrated, but does require a bit more skill and interaction from a player. That all said, I didn't do a full dissection accounting for every source of mana regeneration priests could be utilizing so I shouldn't commit to saying one is better than the other incase I'm overlooking some passive.

Mr. Zusterke, my spreadsheet guru and fact checker, is on holiday at the moment unfortunately =) But he'll be back soon.