Okay, so Graves might be a teensie bit op.
I was skeptical originally of whether he'd be OP or not; but after facing a Graves top, I'd have to say he is, if only a little.

He just auto-pushes the lane, and if you hug your tower, he'll probably just kill you with a Q. Faced one earlier and with just a D-blade he chunked me from full to half in the blink of an eye. That said, its difficult to say how he'll fare in the duo-lane meta.
Honestly, I think there's just a little too much of his power focused in his Q.