Shadow Priest DPS too low

A thread on the forums that's hitting a bit close to home:
http://forums.worldofwarcraft.com/thread.html?topicId=18601081821&sid=1

Particularly this post... Everything he says is EXACTLY where I am, and how I feel:
I never thought I'd be adding my voice to a laundry list of complaints about shadow priests... for a long time, my mantra was "I'm a hybrid class, I offer good raid utility, so I don't have to be at the top of the charts..." but for the last several months, I've watched my DPS plummet, relative to the other members of my guild. Comparatively speaking, my dps is getting worse and worse as my gear gets better and better, and where in Naxx I was sitting comfortably on the dps meters, just below the mages and rogues and more or less even with the other hybrids, I now find myself floundering on the charts, and every time I click on a WWS link, I pray that I did more dps than the tanks (because sometimes I don't).

I don't know how to explain it. I didn't suddenly forget how to play a spriest when Ulduar came out--I work hard to keep my dots ticking and Mind Blast on cooldown at all times, and I know my gear is gemmed and enchanted correctly for the most part (I have an orange gem in my pants that I need to switch for a red, and yes, there are three purple gems when I only need two, but in all three cases the socket bonus is spellpower).

I realize that the fights are more difficult than Lolnaxx, and some of the encounters are not caster friendly, and it also doesn't help that, particularly in our ten-man runs, I am often the only caster dps, which means I am missing out on some raid buffs, but this alone doesn't account for the rapid decline in comparative dps I've been experiencing.

Obviously, we are scaling very poorly with gear at the moment. Part of this is the large amount of haste on everything, since haste has always been more questionable for us than for any other class. As another poster mentioned, having haste translate some way into our dots would be a nice boost and a good place to start.

Spirit is another issue that needs to be looked at. We have to spend five talent points in Twisted Faith to get a measly 10% of our spirit as spellpower, while Holy priests get 25% of their spirit as spellpower for the same investment. At the very least, we need Twisted Faith to be brought up to 25%--I've always thought of speccing Shadow as "going to the Dark Side" for a priest, and the draw of the Dark Side is supposed to be more power, not less :-D At this point, even a 50% spirit to spellpower conversion would not be unreasonable--hell, even warlocks get 30% of spirit as spellpower, and they don't even have to spend any talent points to get it.

Oh, and the "raid utility" argument just doesn't hold water anymore either. There's always a retribution paladin or a survival hunter to provide Replenishment, and Balance druids bring not only 3% hit, but also 3% haste, 5% critical strike chance, +13% magic damage against the boss, and the famous "battle rez," all while crushing us on the dps meters. Even Vampiric Embrace is little more than a joke, except perhaps for keeping yourself alive and giving the healers one less target to worry about. The healing it does for the party is laughable at best--the ret pally in my guild that's always at the top of the dps meter is also beating me on the healing meter :-p

I love playing a priest. I love being able to switch specs and step in to heal when one of our regulars is out. I love being challenged--I switched mains from a mage to this character because I wanted something more dynamic and challenging than just pressing two buttons over and over again. But, the way things are now, every day as a shadow priest is less and less fun and more and more frustrating. I sincerely hope that Blizzard hears our voices and does something to help us out.