In my personal experience, I've found this set too limited in that it only plays the role of a suicide lead--it's hard to bring this 'swine back into the game later on. With the set I am running, I can either open with Mamoswine or keep him back for the mid-game (opting instead to open with Rotom-Wash as a scout) whereas with the Focus Sash Mamoswine I feel like it is an opener and that is it.I personally would run Oblivious (wich now protects from Taunt) and Focus sash: you get your rocks the first turn, then Endeavor anything slower than you if you activated the sash the turn before. Otherwise, you can simply spam Earthquake or go faster with Ice Shard. It typing makes Mamo even immune to weather damage, the only able to do that. So i'd run:
Mamoswine Focus sash
Trait: oblivious
Nature: jolly
Evs: 252 atk, 252 spe, 4 HP
Moves:
-stealth rock
-endeavor
-ice shard
-earthquake
I suppose this is all a matter of personal opinion.