Looks like a generic Ground-type team at first, but when I clicked it I was rather impressed by the Seismitoad and Garchomp set. Good stuff going there tbh. Yeah but like Breloom definitely gives you a pretty hard time and there are stuffs that chould be utilized better in that team.
It seems like Garchomp would be inviting walls such as Slowbro and Porygon2 more than Hippowdon, therefore making Toxic on it a really nifty move. However, this makes Toxic on Hippowdon seem pretty redundant. Stone Edge is also pretty redundant, since you have Mamoswine to hit Flying-types and Excadrill for Ice-types. Setup sweepers can also threaten you pretty well, such as Sub DD Gyarados which can just set up in front of Hippowdon. Best case here would definitely be running
Whirlwind over Toxic. With Whirlwind you can phase a setup sweeper rendering their setups useless.
Another problem I see is Breloom, as it can decimate your team. Best option here would be running
Ice Fang Gliscor with 252 HP / 200 SpD / 56 Spe EVs Jolly Nature. That lets you outspeed Breloom while still retaining respectable SpD. Ice Fang will pressure Flying-types and Grass-types even more, as +2 hurts quite a lot.
Yeah just some nitpicks, team looks really solid. As for other threats, you just need to play properly since it's Monotype.
Hope I helped!