Wow... so much response, thanks everybody!
In the meanwhile, my priest wife has decided to stick with Holy / ImpDS, at least for now when we're still leveling. Her build right now is like this:
http://www.wowhead.com/?talent=bVhbkhxkbZcxtcc0aVz, and while she misses out on Serendipity & all those nice clearcast procs, she gets some more mana, regen, and a notable spellpower boost for the entire group. She also picked Lightwell, just to try out the new version of it.
In any case, we've done some SP & UB runs yesterday, and I felt like God.
It was actually my 1st tanking experience in the new patch, and I hope this doesn't get nerfed, as this is a completely different level of power & feel of play...
We STEAMED through the SP easily with 4 men (2 mages, my priest and myself), without wiping once. The only time we got feared and the healer got killed, I managed to stand through the whole fight (potion, then DP, then LoH) while the mages finished out the remaining mobs. Threat is completely through the roof, and I'm seriously thinking of respeccing improved devotion aura, just to stay alive a little longer while still having no problems with threat. With 3 or more mobs hitting at me, mana is not an issue at all. The only times I was close to running OOM were one- or two-mob fight, when I didn't get hit much enough to regen via BoSanc, and wasn't hurt enough to replenish mana via SA...
After that, we picked up a warlock and ran UB, much to the same effect.
The new Lightwell is AMAZING. Seriously, it is the best thing happened to a Tankadin in terms of healing. The only moments where it doesn't help are fights that require mobility, such as perhaps Nazan in the Ramps. On nore normal fights, including most multi-mob pulls and tank'n'spank bosses, it can pretty well keep me alive for an indefinite period of time. The priest sets the Lightwell in a good place, much like a shaman does with its totems, and then I pull the victims and start the fight near the well. If you ever played a Tankadin, you probably know that it's not a big deal for us to have to click something every 6 seconds, then pushing Tab to return the target to the mob...
Bottom line (not to be offtopic): if there were a Disc priest healing me, I guess I wouldn't feel much of a difference in terms of mana and threat. Still, the healing throughput per second is better for a Holy priest (not to mention Lightwell), and when you tank 10-20 mobs without any CC it is it what stands between your group and a wipe. Still then, my wife had no mana issues at all, even without Serendipity...
