Ah yeah, makes sense. Coop is a huge part. It would be amazing to have stealth classes though but yeah i agree. I play singleplayer alot, and sometimes i do Co-Op with friends.
Don't think a class that's focused on single stealth kills is out of the question, like someone who sneaks near an archvile and kills it before starting a fight, while being generally weaker on straight up fights vs doomguy.