I think Arcanine should have Extremespeed on that set, since, well, it's Extremespeed. It would help make up for the lack of speed EV's too. Giving up one of those coverage moves isn't nice, though....
Why does Hydreigon have Timid if it has a physical attack move? I say go with a -Sp. Defense nature or something.
Aside from that it seems pretty slick, though I did this review a bit quickly so I might have missed something less noticeable.
Not related to the team, but Blissey is much more common then Chansey (which you mentioned a lot), as evidenced by the fact that Chansey dropped into UU.
Also I posted a UU team on the last page if anyone would like to rate that.