The sigs are from http://www.dkpsigs.com/index.php It's supposed to update nightly, but I haven't noticed if it does yet or not.

My priests are all shadow. I found that having one holy in front of 4 shadows made him stick out and get focused fired like a mofo, so I use VE/Plague/Mend to heal in low damage situations and pop them all out for flash heals/prayers of healing in rougher times.

As Wilbur said, I don't instance. I hate instancing for the most part. I hate PvE for the most part. I love killing people.

As for the mana inefficient part, you just have to be smart with not dotting TOO much, and you need my builds which are the most mana efficient builds I could come up with while maintaining shadow damage.

As for the locks, from what I've heard when you lose the priest on a lock team you're in trouble. All of my guys do nice DPS, all of them heal, all of them rez.