Hi, really like your team setup. I just want to give you some advice on Hydreigon.
Myself, I use Substitute. It actually helps out great versus pokemon that can't hurt you. Switch in and make a sub. Protects you against status and Leech Seed.
IF you deceide to use Sub, you should use Leftovers. Expert Belt is overkill, if you have it for Blissey. You'll OHKO it anyway (97.5% - 114.8% damage, with Bold nature and 252 HP), unless it has 252 HP, Bold nature and 252 Def. And, if the Blissey has that, it will still live your Superpower WITH Expert Belt. Also, your power will decrease so you can't kill it with your second hit either and it gets worse every turn after. You might consider Focus Blast for everything that isn't Blissey.
Also Draco Meteor is going to backfire pretty easily if you run a Sub. Sure, its much stronger then Dragon Pulse. But after one hit, Dragon Pulse would do much more damage. You should only run Draco Meteor on Choice Specs or Choice Scarf, as it will nerf Hydreigon big time. Dragon Pulse has much more staying power and will kill any Latios or other dragon when it hits the field, trying to destroy your Sub.
Fire Blast is really superb on Hydreigon. Surf is good replacement, Earthquake is probably not as good as you expect.
Just my two cents :)