Hey, I am not saying that it probably works for you (all) and fills a niche, I am just saying the Destroyer does not really shine as much with Sniper Rifles. :|
Let's say you have a Valiant or a Black Widow. It is obvious that you want to kill more than just the big boss monsters (then you'd rather take a bolt action rifle to abuse weapon damage bonuses), meaning you want goons and mid-tier enemies. You have multi-frag grenades to clear out clusters much more efficiently. You can turn a vast array of guns into heavy damage single-target or multi-target weapons to compensate. It is just the more efficent way of playing Destroyer.
That said, the beauty of ME3 multiplayer is that you don't really have to min-max to play the game, do well AND enjoy it. I was just surprised since those particular Sniper Rifles occured to me to be horribly sub-par.