With the rise of Giratina VSTAR (and Arceus VSTAR, Palkia VSTAR, Dialga VSTAR, and Goodra VSTAR all existing), I've found a deck that can counter it.
Introducing Deoxys VMAX! With 3 Deoxys VMAX and 3 Bastiodons out, you can take 180 less damage from VSTAR Pokemon. And Deoxys VMAX is tanky so it can at least survive against most other decks, just keep it away from Roaring Moon ex and Tera Charizard ex.
Any feedback is welcome. This deck hasn't been tested.