You play pred, right? I can't remember if you play predator or poison..

Poison is basically useless on all but a few maps because of the huge knockback -- their slowness is enough of a balance. The only cons to predator are the knockback and lower health but I think they're really well balanced.

As for weapons, sure, shotguns are overpowered, both damage (500+ damage headshots) and knockback. They're almost at scout knockback level and can constantly be shot, easier to aim and do much more damage.