Campbell is a really difficult player to figure out. He's obviously a supreme athlete and a big play threat. However, in that Urban Meyer offense he basically just ran screens and 9 routes. There isn't much (any?) tape of him running a varied route tree. Some players have come out of that offense and have immediately taken to coaching in an NFL offense (Michael Thomas), while others have been slower in their transition from gadget player to NFL wide receiver (Curtis Samuel).
Especially if the Packers believe he can contribute on ST, I would be fine drafting him at #30 and letting him contribute as a screen/sweep/ST weapon while he develops. But he isn't so incredible that I think he's the "must have" player at that pick. If it's between Campbell at #30 and Samuel at #44, I'd take the latter.