With the changes in 2.3 this spell is even better. I'm getting more damage from plus healing and 30% regen outside the fsr. 8)

As for mana regen in general it's not really that important when AoEing. AoEing isn't an endurance thing like raids. The longer I let things beat on me the more likely I am to die.

Normally everything is dead before I'm out of mana, and if it isn't I was probably going to die anyway. However one little trick I did on really big pulls was to kill a single mob outside of a camp to proc Spirit Tap before charging in. But while it's a neat trick I rarely take the time to do it.

With this setup my biggest downtime comes from waiting for groups of mobs to respawn. My biggest problem related to mana comes from the fact that I'm on a pvp server and somebody decides to screw with me just after a pull. Usually a sheep, double evocate, and the fact that my priest has procced Spirit Tap is enough to take care of things. Pretty rare though since people see three toons and assume there are three players.

While the spell overall isn't that great, and even most holy heavy specced priests skip it, in this particular situation the synergy is amazing. By using arcane explosion I am getting 100% damage output from both mages, instead of the single reticule targeted aoe while the other mage does nothing. It makes things go much faster.

Anyway, with any other setup besides following mages around I probably wouldn't pick up Holy Nova either but the synergy is really good and I would definitely recommend picking it up if you are boxing a similar group.