It definitely has a place in expanded, it does generally have good matchups, being able to counter Trev like you said, night march with giant water shuriken and ability lock, and can generally get setup in many matchups. It's biggest issue right now is golisopod, which I've been seeing a lot of in expanded, with either zoroark or garbodor, both of which are really threatening to greninja. Regardless I don't have doubts that it's at least a viable deck right now.