First issue I see with this team is your Starmie. The problem with this set is the lack of recovery and hazards will wear this team down very fast since your starmie can't last long with this set. Plus, I suggest changing her spread to EVs: 168 HP / 108 SAtk / 232 Spd. The given EVs allows you to get minimal stealth rock damage, the speed allows you to outrun scrafty after a dd (you can bump it to max if you feel like speed ties with another starmies and raikous are important). Also helps switching on things like Terrakion's Close Combat. The remain EVs are bumped into Special Attack. Also I agree on Recover > Blizzard and I would use Scald > Hydro Pump first change is to keep starmie healthy because you will need her alot. Scald is for try getting timed burns on things like Tyranitar switch ins, Ferrothorn switch ins, awlays a plus.
I think you're overrating the air baloon on heatran. Its main prupose is check dragons, wich you already have enough cover. Ice Shard on Aboma, Bullet on Scizor helps, 2 Steels, Intimidate... yeah, its not that of a huge issue. In counterpart things like Tornadus will run rampant against this team if he gets a grip since your only hurricane switch is heatran wich has no special defense investiment, same draco meteors from latios (though scizor can pursuit this one, you must avoid hp fires though) and hydreigon. You mentioned the air baloon is for dugtrio as well, but your main boys against sun is salamence and kyurem, wich can run rampant against sun, as you can protect heatran from dugtrio until you really need to use him for check something. regardless of the baloon, sun will be a hard matchup though (as it is for any hail team). So a special defense set will help you better. Change you Heatran to 252 HP | 4 SAtk | 252 SDef with a Calm Nature, Lava Plume, Protect, Stealth Rock, Roar.
Nice team, and good luck.