If, the sylveon player has infinite syveons set up and ready to go, the this happens:
P1: sylveon GX attack, remove two ninjas
P2: active attacks + band = 110 ability to bench sylveon and sets up froakies.
P1: attacks normal 110
P2: ability to active KO and ability to bench sylveon put it at 120 damage on set up frogadiers
P1: attacks for ko
P2: evolve for two ninjas and then attacks for ko
P1: advances nsxt sylveon and attacks
P2: evolves to break, ability for 60 to active retreat ability to active, attack for ko and 6th prize
I don't see the threat of hard to power up 200hp 110 damage attackers as long as they're not consistently searching for 3 cards a turn. Of course, unless they hex stream without searching for hex with their attack.
Edit: when I wrote this I was forgetting hand disruption. Team skull Grunt and delinquent can really mess stuff up for greninja, even though field disruption doesn't do anything.