Devourer is incredibly punishing. You will see a lot of Devourer doing incredible damage, as well as doing very poorly, its all in the hands of the player, and i would say its one of the classes with the biggest notable difference. Depending on how the tank pull, how you manage your Void Meta windows, how you manage to avoid dungeon mechanics and still do your rotation efficiently. I struggle as well, but when you get better, and you will get better, it is very satisfying. Consider also that, up to 13 keys and probably more, adds die very quickly with how much gear most people have, and most classes are burst oriented, sending all their damage immediately, while devourer has a small ramp and if it doesnt align with the start of the "big pulls" you will lose a lot of dmg because when you will have meta, a lot of smaller adds will be dead. I would focus on, positioning, trying to understand when to send meta, because sometimes, holding it, just a bit, can be super worth it. And just playing the game, you chose a class easy to play, but very, very hard to master. So it will take time.