Priest by about a million miles.
As I said, I agree that it’s boring. Having watched a lot of games in GM and beaten a lot of priests I can say with anecdotal evidence that it’s not a brainless deck.
A lot of times the hardest thing about beating priest is not giving up out of boredom.
The only priest I’ll ever play is buff tempo, but it doesn’t have enough support so can’t really be played right now. Give it more card draw and we’ll see.
In the end, we both want that same thing.
It sounds like we can agree to agree on that score. 
I really wish we could see another dynamic to priest. I find myself avoiding playing meta decks because they just feel so filthy.
Most definitely all forms of priest… followed by freeze mage and in wild resurrect big demon warlock… And mostly all mooneater decks…
Any deck that messes with my deck. Like stupid mill Druid, Rogue or Lock.
Immediate concede from me.
I dont mind aggro. But ressurect priest (wild) and somewhat standard. Exodia mage, or different versions of the infinite zero mana fireball deck, Mechathun, and other meme one turn kill decks in general. Mill Rogue, etc…
anything i lost to 
Priest by far in my opinion. Either way its too much heal, or a way too much rez. Its really annoying that you bring them to 5hp, setting up for the final blow, than bang full heal, again bring him to 5 hp than bang full heal again. Same for the rez priest.
Probably priest, I just gquit when I face them!
For me probibly the new meta warrior decks. They just spam armor and dont even play minions till turn 7 (it seems like turn 7) most the time. Paladin is boring to play against as well its so predictable.
Resurrect priest (Wild) is the equivalent of sleep paralysis.
Skillless snoozefest to the very bitter end.
Also Secret Mage, thanks i want to play the game, jesus christ.
imho, turtle mage has now become the most boring deck i’ve played against recently… and i know its players are also bored to death, playing with it as well…
but its a one sided deck, like how the original quest rogue was… so maybe we’ll get some changes that render it obsolete… or maybe i’ll just have to start playing aggro against it… one of the two… lol…
For me it’s not so much the class, it’s the current mechanics that make the game not fun and boring namely mana cheat, endless discovery and too swingy. Some may find this attractive, but I’m not one of them.
Definitely turtle mage.
Oh boy, can’t wait for you to do the SAME THING EVERY TURN for the last X turns.
I find Mage boring sometimes
Also Priest when they resurrect the same minion 6x’s
If all the classes didn’t adopt LOE discover keyword i would find Mage super boring.
I would say priest is extremely boring to play against because you know at the start of the game that you will just be killing Convincing Infiltrator again and again. I run a Galakrond Rogue deck that beats them but it wins by running them down slowly. Every time I play priest with that deck I know I won’t win until turn 35… it’s kills just a small part of my soul.
Also, I have to say that the copy priest is annoying. I hate being beaten by my own deck concept. Though I do have to admit that when I’m holding a hand full of bombs and they use Madam Lazul to find only something weak like a lackey or some other junk, it is intensely satisfying.
Priest. Let’s bring back every minion we play 10 times. Yeah, so annoying.
Turtle mage for sure. What a boring way to lose.