I'm not saying this to rub salt in the wound, but you really should keep at it, as the sniper is worth it. Sure, it's pink and whatnot, but it comes in handy against wizards and everything weak to solar. I really like it and has saved my ass many times. Nexus, for instance, drops like a fly to it, even on Nightfall. Just keep rerolling the mission until it lands on Restoration, it can be done in less than 10 min, and as far as I know, the mission you complete has no relation to the reward whatsoever.
I know it can be frustrating as fuck (did like 10 missions, got a helmet, the sniper, and 8 chest pieces in a row) but eventually you should get it..