Although I'm not well invested the OU metagame right now, I can criticize this team quite easily, due to the fact that it looks like some higher level players would call "Mexican Offense". It's basically offense + Blissey/Chansey. To be quite frank, Chansey kills any type of momentum you get, and allows the opponent to take control of the battle from there, unless there are only special attackers left.
Possible changes worth considering:
Change Sub -> Icy Wind on Gengar. This nets you an OHKO on Landorus formes, and Gliscor as well iirc.
Change Chansey -> Hippowdown, to better deal with Talonflame, Lopunny, and Metagross.
Change Forretress -> Bulky Starmie.
Starmie @ Leftovers
Ability: Natural Cure
EVs: 248 HP / 252 Spe / 8 Def
Timid Nature
- Scald
- Reflect Type / Psyshock
- Rapid Spin
- Recover
Reflect type lets you spin on Bisharp and Tyranitar safely without getting pursuit trapped, while psyshock gives you a definitive answer to LO Gengar (the 4 SpA evs arent a requirement anymore since most gengar run LO + 29 HP Ivs) and SubCM Keldeo.