Great team, not that much to say about this.
Im not a fan of heatran in weatheless team, because i think that if you are facing a rain team Heatran cant find so many chance to setup stealth rocks, and if it does tentacruel and starmie commonly seen in rain teams can spin them away easily, and also you obviously have your main move weakened. To fix this somewhat, i think that a random weather changing move can help. I would put Sandstorm instead of earthquake on terrakion, because you know that earthquake doesnt hit anything relevant, while sandstorm gives u an advantage if your opponent already sacrificed his weather changer. This is just my opinion though, its optional.
Another little fix that i would do is to replace Reflect on Xatu with Toxic. The win condition of this team is to sweep with latias i suppose, so cripple Tyranitar with toxic helps your latias toxic stalling it. Toxic also force Blissey and chansey to switch-out, which can come in handy since they can ppstall you otherwhise.
I would also give more speed on xatu to outspeed Tentacruel and Breloom, something like this spread should work EVs: 248 HP / 200 Def / 60 Spd
Hope i helped, luvdisc'd anyway xd and gratz for the badge!