Is it intentional that tanking specs do nearly as much (or more damage) than dps specs of the same class? I'm wondering why anyone would choose a dps spec.
For starters, if you're not outdamaging the tank you're doing something wrong. Tanks can do a decent chunk of damage in 5 man dungeons, especially while leveling. But in any kind of non-trivial content with competent DPS they will be at the bottom. Right now is especially weird because people aren't used to new rotations/abilities or they might not have their artifact leveled. I know I could barely stay above the tank when I did halls of valor as Unholy because I had NO idea what I was doing.
Second, the primary characteristic of a tank, above even their survivability, is that they generate a lot of aggro. Having mobs bouncing around unpredictably is usually not a good thing. I'm sure in normal mode 5 mans you could probably send in 5 tanks and laugh at everything though.
As for why they do a lot of damage - it wasn't always this way. For example Revenge used to do effectively no damage but it had a huge threat modifier on it. Warriors would hold aggro by spamming sunder armor (no damage) on everything. At one point Blizzard realized that some people might want to quest or even PVP as a tank so they removed the extra threat mechanic and either replaced or made those abilities do extra damage while giving tanks overall much higher threat generation. They still don't compare to DPS but it's quite viable to do quests as one especially if you're making big pulls.
All that said...I'm fully expecting to top the meters in the first 5 man I tank with randoms. That's usually how it works out.
I wonder what will happen to the artifact weapons in the next expansion.
I'll laugh if we just get to vendor them.
What I'd like to see is for them to carry forward, but have them give a second artifact for each spec. Have them be sidegrades with different playstyles. Would be a balancing nightmare I guess but hey whatever.