The one thing about A-Exeggutor ex is that if it does see play, the Drago mirror actually becomes really, really awkward. Like more awkward than it already is. Anything that isn't a 2-prize KO is now much easier to pull ahead against, and even something like Goodra or even Dragapult loses its merit as Giratina VStar and A-Exeggutor ex guarantee 2-prize KOs in some shape or form. If you use Rolling Iron to prevent your Drago VStar from getting Knocked out, well now the opponent just uses A-Exeggutor's attack to take something on the bench instead. Now, the person who used Rolling Iron is behind in the prize race and has to play to either take 4 prizes in 1 turn with Dragapult, or stop the opponent from attacking with a Regidrago VStar at all next turn. If the person who used Rolling Iron had used Giratina or A-Exeggutor, they would have been ahead in the prize race and taken out a Regidrago V prior. Goodra becomes a lot less effective in shifting the momentum of the game, and we'd likely see a lot of games that play out like a Raging Bolt mirror or Roaring Moon mirror where it is just trading 2 prize KOs with no other plan.