Why not just play Rotom with Dual Trans instead of Garchomp? It'd be way more efficient and free up a lot of space for you.
You could also run Spiritomb and just charge a Giratina up manually; then, when you are ready to break the Trainer lock and attack, play another Giratina to the Bench, use Let Loose, and return all the Trainers they've been forced to hold to their deck.
Consider adding SSU, run 3 Let Loose Giratina and some Premier Balls, and drop the Uxie count down so you have room for Claydol. A tech Mesprit or two could also be effective, allowing you to shut off their Claydol for a turn or two (with the aid of SSU) while you kill it with spread. I also don't think you need Azelf lv. X.
You need an answer to Nidoqueen if you plan to actually run this for Cities. You could tech in Dialga G lv. X, or try Devoluter, although it probably wouldn't be effective due to its unsearchability and the fact that it uses up your attack for the turn. I'm not sure what other options you'd have to counter it, but you definitely do need something.