Playing damnation, I’m pretty sure K12 is an overall better setup, or arguably weapons that can deal simple shooters faster on vet faster (and that’s like basically every weapon outside of plasma, revolver).
I also don’t get the anti-fun factor. Outside of low-int, there is no chance in hell that bolter will clear even all elites. There is always something to do.
For flamer (which I think is too much and should be nerfed) it might be a preference thing, but I don’t feel that either, and I had a few runs with “blaze away” teammates deleting mauler in a few seconds. If the situation is fine I let others have fun and just cover their backside, otherwise, I can just do whatever else.
Let me give you another example, you are running an ogryn with Paul because you want to bonk ogryns. If I’m running plasma the most you will bonk is opening up the shield for me with it, and plasma is pretty bad. A similar thing can happen when running a lot of other specialized weapons.