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.