Truthfully, we don’t know anything concrete about the Jailer other than his looks. And therefore, I can only criticize his looks. We will get to criticize his story, plot and goals once we get there lol
And as far as appearances go… he is a shirtless muscleman.
Like the villains of tBC, Illidan and Kil’jaeden.
Or the villain of MoP, Garrosh.
Or the villain of WoD, Archimonde.
Or the villain of Legion, Argus.
And look, there’s nothing wrong with being a shirtless muscleman. I mean, I am one myself.
https://i.imgur.com/bD9bj3w.png
But so far we’ve had 8 expansions and 5 of them ended with us fighting shirtless musclemen. The other 3 had a dragon, a tentacle monster and a shirtful muscleman.
The Jailer could be anything else. He could have been a big skeleton grim reaper.
He could have been a lady, like the Marvel Comics version of Death.
He could have been a withered old man, to really sell the idea that we were fighting the scariest aspects of Death itself.
But nope. Yet another shirtless muscleman for a boss.
And I’m not saying that’s necessarily bad, but it could have been less repetitive and more creative. I hope the next end boss isn’t a shirtless muscleman.
Maybe the next protagonist could be one instead! 
