For a while now I've been running around dual specced, with Shadow as my alternate. For grinding it doesn't actually make a big difference and in fact my old Disc Hybrid spec was in many ways more durable. The problem was, that spec was tweaked for survivability and soloing, and I really needed to step up my healing game. Thus, the full-on Disc spec I sport today when I go in for raiding, and shadow spec for soloing.
I have to be honest - I didn't like Shadow spec at all when I tried it around level 50. Even then, Holy/Disc hybrid seemed to carry a lot more oomph, have less down time, and have a higher survival rate. So I adopted that new (home-grown, I proudly add) spec fully, and pretty much sailed through content from then on.
Still, I am well aware of many successful shadow priests out there, so I did some research. What I came up with appeared to be a viable DPS build. The beauty of this build and Disc is that both share a lot of attributes between them in terms of what gear is good. Right now, I'm focused on Spell Power because it's rare that I'll run out of mana during the run of the mill fight anyway. Both like Crit, too - crit heals or crit DPS, we like it all. The down side is that +hit gear is not of any use to the Disc build, and usually takes away from what I need to keep up the healz.
I figured out a rotation, a solo rotation, set up my keys, and proceeded to play around. Still, it was unlikely I'd raid in this spec. Heals are what I do, generally.
Until last night.
Two heroics - UK and UP - gave me insight into my damage potential as a shadow priest, and I am rather impressed with the numbers. There was me, an ungeared DK, and a Naxx geared boomkin. The boomkin was head and shoulders above everyone in DPS, but I came in second with 1650-ish numbers, better than either Grimm or Flora can post right now. And there were misses a-plenty.
Of course, you have to account for the fact that I'm rocking Naxx epics all over the place here. Grimm and Flora have seen Heroics and that's about it.
We have a fledgling priest in the guild that intends to go full on Shadow for raiding. I whispered him after our runs to let him know what kind of numbers we're seeing and he was happy. So we'll see how that works out. It would be nice to have an SP next to me, especially if we can get him to dual spec Disc as well.
And possibly in a future Naxx-25, I'll slip into shadow form and we'll tank Raz together.