Few questions about DPS classes in WOTLK

Hello everyone, I am a long-time Warmane player, started on Cata way back 2012. Been active on MoP for a year after the moltdown, and now trying WotLK for the first time.

So, if I may ask, what would be the top dps classes in WotLK? I'm mainly looking to do PvE content on Icecrown, and the classes i'm interested to play right now are Shadow Priest, Mage, Warlock, Shaman or DK. What would be the best among them? I have researched quite a bit and saw that Shadowmourne-wielding classes would be the best as they say, but I don't want to play a Paladin or Warrior.

And since I mained a Shadow Priest in Cata for the longest time, how are they in end-game raids? Are they good? Do they do good dps? Or they are just unprioritized and best replaced with another ranged dps?

Thank you in advance for answering my questions!

Shadow Priests are fine. Average single target DPS, superb Multi-target and AoE DPS. And they bring some very nice utility: a boat load of passive group healing, and even stronger on-demand off-healing when it's needed. They aren't a DPS chart topper unless they're able to take advantage of their multi-target damage tools in some way.

As for other classes, hmm.

My opinion, from having both played and having seen others play these classes at a high level, the DPS rankings would be (vaguely) something like this:

Top tier: Fury Warriors, Mages, Rogues

In the hands of skilled players, these classes will see very little competition unless some aspect of a fight plays very heavily to the strengths of some other class.

2nd tier: FDKs, Aff Locks, Feral Druids, MM Hunters, Ret Pallies, and maybe a couple other specs that don't occur to me right now.

When I say 2nd tier, I mean that these classes are also capable of superb output and top the charts a lot of the time. Just that, gear and skill being equal, they are typically outmatched.