Mamoswine is pretty similar with Nido family. Both have similar speed, eat balanced cores alive, can't boost their stats (this is a very important one which differs Mamo from Diggersby and Crawdunt), have very little counters and both have the luxury to carry a random coverage move on their fourth moveslot to lure their counters (Mamo can run SE for Rotom-H, Knock Off for Cress, Freeze Dry for Alomomola, Superpower for P2 while Nidos can go Fire Blast for Bronzong, Superpower for Blissey/P2/Umbreon, Megahorn for Cress/Umbreon, Thunderbolt for Mantine/Vaporeon/Suicune after couple CM). Mamoswine just exchanges a STAB priority (makes it harder to revenge kill) for a shittier typing defensively (makes it easier to revenge kill).
I think Mamoswine is fine in the tier. It's just that people are scared or biased about it because Mamo has always been OU since its introduction. Same thing happened when Lucario and Infernape dropped for the first time. Everybody freaked out, lost their minds, shit their pants but got used to them in due time. A suspect for Feraligatr, Pidegeotite or even Heracross would be more accurate in my eyes but i wouldn't cry if they didn't happen either.
I think Mamoswine is fine in the tier. It's just that people are scared or biased about it because Mamo has always been OU since its introduction. Same thing happened when Lucario and Infernape dropped for the first time. Everybody freaked out, lost their minds, shit their pants but got used to them in due time. A suspect for Feraligatr, Pidegeotite or even Heracross would be more accurate in my eyes but i wouldn't cry if they didn't happen either.