The biggest problem I see with this team is the fact that you're lacking firepower or win conditions. Any last mon mono-attacking Calm Mind Arceus with Refresh will just end up destroying you (Dark Arceus, Water Arceus, etc). Your opponent can easily just sac every Pokemon on their team, then bring in Arceus and you cannot do ANYTHING to it. You are also relatively weak to Manaphy, although Ferrothorn works well, I guess. Probably the easiest way to solve this problem is to just stick Perish Song on Arceus, I suppose.
Furai i rule f****s
20:09 Melee_Mewtwo wow
20:09 Melee_Mewtwo the furry is lord of the gays