starmie is outsped and killed by gyarados after 1 dd. he'll usually be blowing up on cresselia, who happens to be 2HKO'd by ddlo gyara, and honestly, where the hell is machamp gonna find the time to switch in? the only thing he can really switch in on is garchomp's stone edge. garchomp outrage kills non-superdefensive starmie (and 2HKO's superdefensive starmie easily), and honestly, the superdefensive ones don't run ice beam. starmie has no place to switch in, except against ape, who's usually dead early on. also, starmie will not be doing anything to metagross who can pursuit it for big damage.A rather solid team. There are no real weaknesses here since all your Pokemon cover each other's weaknesses well.
There are a few pokemon that you will have to outmanuever though ( i'm picking at straws mostly). If Metagross goes down, Starmie could wipe out many of your biggest threats. I'm not sure whether full HP bulkymence survives Starmie's ice beam but I think it doesn't and Gyrados require 2 DD to outspeed Starmie. Starmie can take Ape down easily as well as Garchomp if its locked in Outrage. Similarly, Cressellia can hurt your team as well. Of course, Deoxys can take care of both but its something to be aware of.
Machamp is a mild threat, scoring supereffective hits on Mence, Chomp, Gyarados, and Deoxys-E (since it lacks Psychic).
edit: lol taylor finished his post faster than me