I certainly don't think they're done with Hill after one year, but it's pretty darn evident it was a mistake using a 2nd rounder on him. They have no confident in Hill right now, at least to start. And obviously, they just needed bodies at DT, period, no matter who it was.
I do think Hill and other draft picks and signings were plenty reason why it was time to move on from Marinelli.
I remember being a Marinelli fan when he was first brought in, but that dwindled over the years. It started at, "alright, we got a DC with a excellent track record." It transitioned to, "Well...at least he's still knows how to mold his defensive lineman." To finally, in the last year or so, "Yeah...I think the game has passed Marinelli."