Manaphy is a little hard to deal with for this team since it can absorb a lot of hits and setup tail glow but you do have ways to beat it like medicham speed tieing or just straight up outspeeding most manaphys, non energy ball manaphy getting walled by rotom and torn + weavile to outspeed.
This beast is by far the biggest threat to this team if it has the right set, which is modest life orb hp ground your best bet is to just setup hazards and pressure it as much as you can with fake out support and making sure torn and garchomp are very healthy.