Exeggutor-Alola of G-Luke:
I think the sets that can switch attacks ( like Z move ) are the ones that will completely crap on defense. Leaf Storm / Draco Meteor / Superpower / Synthesis basically craps on everything defensive but Magearna and SpD M-Scizor, who both have to fear other options that it has. Any kind of balance team with say, Landorus-T as its revenge killer could get screwed if it gets one or two defense boosts. Unaware Clefable can't handle two Leaf Storms, and Quagsire obviously can't. It's managable if everyone just runs offense but that's obviously an unhealthy situation.
Rhydon of Pika Xreme:
You say it doesn't have recovery but it has Wish. It also gets Swords Dance and Pixilate Quick Attack, which is probably a more relevant reason why its insane combo of bulk and power is wack.
Pika has already opted to remove Wish, but I still am skeptical it is balanced for reasons such as the ones you stated