Cool deck, though it's the first time I see Tyranitar without Weavile SW. Your beast needs a ton of Energy to move, Weavile can charge him really fast with its Shadow Charge and I'd recommend it. If you don't want/have Weavile, consider using Spiritomb AR over Sableye as a starter, stalling your opponent until you get Tyranitar ready.
About Blissey, I don't really know if it's that useful, since you already play Rare Candies, a 1-0-1 Nidoqueen RR line would be really better for healing imo.
Another card I would say is necessary is Lucian's Assignment. Tyranitar needs a lot of energy, if one is KO'd you would have to stall until you get a second one running. With Lucian, you can move the energy before dying and retreat to another Tyranitar thanks to Moonlight Stadium.
So, all in all:
-1 Darkrai MD
-2 Level Max
-1 Premier Ball
-1 Expert Belt
+2 Lucian's Assignment
+1 Azelf LA
+3 Warp Point
Ok, some may seem strange. I don't think Level Max and Premier Ball are needed, with Moonlight Stadium Darkrai can easily switch in and out in order to level up. Plus, Darkrai X isn't weak, its attack is awesome, he can attack for a turn or two. SSU again isn't that needed, you can just move the energy with Lucian and retreat. Warp Points are really useful in every deck, they have saved me in numerous situations. Azelf is pretty much needed, in case your single Darkrai X is prized. Well, that's what I would play anyway.