This is just your opinion however, and what worked for your team, IMO I think that shotguns are more OP than snipers because you usually do not have do much aiming, and they have ridiculous range(Conspiracy Theory). It 100% takes more skill to snipe in any game mode because in order to get the reliable kill it must be a head shot, and even with the large hit box and high AA, you still have less than half of the target that shotguns do, for example, I can one hit kill you with a shotgun if I shoot you in the toe from a range double double that of warlock melee (cough, conspiracy theory D cough) but with a sniper it has to be a head shot which all in all is about 1/6-1/10 of a gaurdian's body.