To be honest, your team is a collection of strong pokemon that all have the same advantages/disadvantages. Your team is very weak against ice. Your garchomp, dragonite, and haraxorus are all weak to it (the first two are x4 weak), and you don't have anything to really counter that weakness. Many of your pokemon also have the same move types, preventing them from countering opponents and serve the same purpose in your team overall as they have strong attacks.
Your Gyarados has a stong attack.
Waterfall (rather than surf because of your high attack)
Earthquake (also good with the attack and will counter electric, your nemesis)
Avalanch (once again, opposed to other special attack ide moves because your attack is probably more than 2x higher than your special attack)
Your Haxorus has a lot of the same type moves and is a strong attack pokemon. It doesn't really add anything to your team. I'd replace it with a Hydreigon which has both a high special attack and a decent attack. Teach it
Dark Pulse (an egg move!)
Tyranitar (also strong attack)
Flamethrower (although a special attack, you should have a decent special attack stat and it will help counter steel, bug, and grass)
Although stone edge has STAB, it is somewhat unreliable and I think as your gyarados now has earthquake and stone edge, you should mix up the move type.
Try to diversify your excadrills moves. Again, the moves cater to a strong attack.
Your Garchomp does nothing that your Tyranitar can't do.
Concider a Gardevoir (as much as I love Gallade, your special attack needs more focus) Teach it
I feel bad saying it, but your dragonite also does nothing your other pokemon cannot do. As the team I set up has some weakness to bug, for a last pokemon I would go with a fire pokemon. I think a Volcarona would do you well.
While rock pokemon pose a problem to Volcarona, as a whole your team would be able to combat them with magical leaf, surf, waterfall, and earthquake.
If this response has offended you, I'm sorry, but I'm offering my best advice to help you improve your team.