There are four variations of Mamoswine in the Battle Tower;
465 | Mamoswine | Adamant | Icy Rock | Earthquake | Ice Fang | Peck | Hail | HP/Atk
601 | Mamoswine | Adamant | Sitrus Berry | Avalanche | Earthquake | Iron Head | Curse | HP/Atk
737 | Mamoswine | Adamant | Lax Incense | Earthquake | Superpower | Fissure | Hail | HP/Atk
873 | Mamoswine | Adamant | Life Orb | Earthquake | Ice Fang | Stone Edge | Double-Edge | HP/Atk
all of which are pretty dangerous. If you want to be able to take on Ice types without losing to Mamosine and Weavile then I'd recommend a Fighting type. Lucario is a very nice sweeper, but it's open to Mamo and, assuming you'd use Swords Dance on it, Garchomp pulls off that job much better.
Just looking at the members of your team, I can tell that Drifblim is the weak link unless you're using a gimmicky TrickScarf set, assuming it's even able to run that at all, I can't quite remember if it gets Trick or not. Even if it is the TrickScarf one, imo having two Ice weaknesses, or two shared weaknesses at all for that matter, on one Battle Tower team is a bad idea; you simply don't have enough space for members to be sharing weaknesses. You might want to address this too.
If you gave me some movesets which you're using, I might be able to help a bit more if you don't want to make your own thread.