Shammies are definately more of a primary dps slash healer now. All premise of offtanking was removed. We are glass cannons that can heal, which is what the class was meant to do from day 1.
DK tanks will be relegated to playing around in the shadows of the established tanks, and DK dps fighting for spots with a million other dps DK's never mind all the other dps classes - which is basically all of them now. It's not going to be a pleasant place to be, I think. Only those who truly excel at the class wil get anywhere. Offtanks? Druids are better, they can dps just as well and still heal, cleanse, battlerez, innervate - without having to go out of combat to switch presence or gear. DK's can buff and dps when they aren't offtanking something and that's about it. When dps'ing they can't really fill a shaman or druids or paladin's role. Basically when tanking they're competing with 3 existing tanks. When dps'ing they're competiting with the likes of DPS warriors and rogues which are 'pure' dps and don't bring things like cleansing and offhealing capabilities to the raid. So this is why I'm certain there's going to be a lot of DK qq. They're filling the old role of Enhancement shammies and enhancement shammies are moving more to pure dps because they now have pretty decent sustained aoe and single target dps thanks to maelstrom weapon (which allows you to shift what you're doing on the fly.. need single target dps? throw out those lightning bolts.. need some aoe? churn out the chain lightnings... healers taking a little strain? start flinging chain heals) and have a pretty good cc at 80, a ranged sap if you will which is nothing to sneeze at.
Would i want to fill the 'old Enhance shammies' shoes again? Not really. It sucked compared to the new and improved Wrath enhancement shaman. There's only room for so many of them in a raid, and the difference is, now, there aren't many shamans around at all, our totems still kick ass, we still have some of the best buffs and can uff anything and anyone appropriately without having to spec for it. You'll see a large percentage of the shaman base getting raid spots while the legion of dps dk's get sidelined. Expect to see emo in quantities, if not already. I just hope the DK tears don't cause them to nerf my shammy. It's been along time coming but I'm finally enjoying the class again. If those emo-kids-in-plate ruin it for me, there will be a reckoning.