Hey, cool team.
First of all, i'd like to suggest Roar > Earthquake on Heatran. And using Stealth Rocks > Protect. A combination of Stealth Rocks + Roar deals with Volcarona way better than Earthquake. And since you carry Air Balloon, Protect seems unnecessary. You might also want to change it's ev spread to a special defensive set. Thundurus-t seems like a pain to your team, so an ev spread of 248 HP / 252 Sp Def / 8 Speed along with an calm nature. You might want to change your item as well if you're running air balloon for subtoxic Gliscor since Gengar does exactly the same job. And earthquake doesn't seem like a big problem with 2 resists while having Forretress too. So try Leftovers > Air Balloon. Now that you have Stealth Rocks on Heatran, you get an extra moveslot on Forretress. I agree with evillocke that Toxic Spikes aren't as good in bw2 as they were in past metagames so I would suggest to change Toxic Spikes > Spikes and then using Volt Switch > Stealth Rocks. Having a spin blocker (Gengar) works better with Spikes as well, since Toxic Spikes can be removed without using Rapid Spin. Next up, change Latias to Latios if you're going to use a scarf set. The difference in Special Defense is almost unnoticable while the difference in Sp Atk is a pain. (for example missing out on the ohko on Terrakion and Keldeo). I'd also like to suggest Draco Meteor > Dragon Pulse on Latios. The fact that Latias is choiced means it'll have to switch out nearly every time it attacks, therefore Draco Meteor seems like the better choice. It also ohko's Tornadus-T after any previous damage (from 98%). Also, use Low Sweep > Drain Punch on Breloom. Low Sweep is stronger due to technician and lowers the opponent's speed, giving you the possibility to out speed and 2hko a lot of stuff in OU.