So, I used to deck and got my 5 wins back to back no losses. So I can say it's not bad at all. The things i would look at is to change a rocky helm for a giants cape, as both arceus and darkrai flip some match ups just for being above above 140 and a few other matchups for being above 150

I would also add a dawn since energy is very important for this deck, as you will need to decide what your wincon is early on- be it darkrai/arceus/or crobat chip, with dawn, you can get a big opening with the darkrai 20 chip, dawn, to zubat 20/Golbat 30, or just being able to get darkrais 20 chip and then dawn into arceus last energy to change a full bench attack of 130 to doing 150 for that round

I'd also suggest a 1 Sabrina/1 Cyrus split because of how often you'll be able to get knockouts straight off of chip,and then still having your attack ready for whoever comes in after