This is a very solid Sandstorm team you have here, I like the use of Deoxys-S in this team. However I have a better use for it. Looking at your team, I have noticed you have nothing to take on opposing Genesects. Scarf Variants U-Turn out from Chandelures and then trap you with Tyranitar. Celebi lacking Hidden Power [Fire] also means it can force switches very easily with it's powerful U-Turn. Your Genesect in itself can only check it at best at once it takes Life Orb Recoil, your opponent knows that they outspeed and can OHKO with Flamethrower. To combat this, I recommend changing your Deoxys set
around a little.
This set may seem unorthodox at first, but it's really quite effective. It patches up a lot of problems that I can see with your team as well as providing hazards support for Excadrill and friends. 12 Atk EVs ensure the OHKO on Tyranitar with Superpower, for the times when you think Chandelure may be useful to you and you don't want your opponent getting Rocks up. 72 SAtk EVs guarantee you OHKO 0 HP/4 SDef Genesect with Hidden Power [Fire]. 204 Speed EVs put you at 490 Speed, always outspeeding scarf Genesect by 1 point. Finally, the rest go into HP to help check SD Breloom who is a problem to a lot of teams.
Another thing I have noticed is how much you rely on Excadrill to sweep with this team. From what I've seen, Air Balloon Excadrill generally needs a Swords Dance before it can do anything and even then it gets shut down by a lot of things. What I'm trying to say here is that there is a lot of pressure on Excadrill to defeat a lot things your team has trouble with. I also noticed earlier about Genesect, even though Life Orb may be cool to grant you some extra KO's, it gives away the bluff of a potential Scarf or even Focus Sash. You also mentioned Genesect being slow, why not try a Rock Polish Genesect?
It takes some of the pressure off of Excadrill to sweep, as well as checking opposing Excadrills who are very troublesome for your team.
This set utilizes all of Genesects offensive traits brilliantly. The lack of U-Turn here really isn't notable, when after a Rock Polish you outspeed pretty much all of the Dream World Metagame. This set transforms Genesect into one of the best revenge killers around, coupled with Deoxys's hazards and a Rock Polish you can beat a lot of Genesects "checks" such as Garchomp, Chandelure and Excadrill.
I also agree with Kidogo on the fact your team is weak to Rain. With no Recover, Celebi can't constantly come in on Keldeo / Manaphy and stop the offensive prowess of Rain Teams in general. I was going to recommend a bulkier Celebi set, however I have something much more effective in mind...
patches up your Rain Weakness well. A somewhat underrated Pokemon has a great niche in this current Metagame, from much testing I have found it to be the most solid answer to Manaphy. It removes your massive Water weakness and gives you a solid answer to Rain mons spamming Hydro Pump. It's also nice to have one less team member Chandelure bait.
Good luck, hope I helped!