Mages can portal round the world, rogues can vanish out of a fight they're losing, locks can instantfear and run with the speed of light away.
Most classes have some advantages over the others, which is why not everybody play "the OP class".
I know DKs was considered around the worst tanking-class on average in cata due to the rng. I found them very strong myself, and now they got buffed because so many thought they needed it, and are, as far as i know, the best MT-class now, which have made my face into a permanent grin.
They weren't bad because of RNG. They were bad because keeping STD's up was difficult and they took more damage than other tanks because of less avoidance. Which was fixed in 4.3 with the Outbreak hotfix and the shift to a passive effect of Blade Barrier, among other things.
On the other hand they could solotank baleroc.
I know the arguments for it. I just think most people made it a lot worse than it was. And now they made them stronger to suit the more average playerbase that have a hard time managing the selfheals and CDs.
Passive blade barrier was a horrible design. It didn't allow you to game RE(thank god that's no longer needed) and thus made you lose a lot of Death Strikes.
If you really care that much about what people will think of you for playing a certain class, work on your self esteem.
DK's are weaker than they've been in the past, and their reputation still hasn't changed and probably won't, the same way huntards are always going to be huntarded even after blizzard stupid-proofs their abilities.
It's like crossing an intersection. There's shit going on all over the place and you don't panic and act like an idiot then do you?
Who gives a shit what the mouthbreathing masses think? Everyone thinks every class (or spec, for that matter) other than the one they are currently playing is 'faceroll'.