I disagree, I think it was a gamble because Fitz was banking on Bahl taking a step, others maintaining their level whilst having a number of new partnerships at that back end and Luke elevating his defensive game. None of that was even close to a given.
Personally I would have kept Graves, even at what he got from Pitsburgh (and I think he might have taken less to stay here on what should have been a strong team). Given the free cap space and not singing Miller and one of Smith or Nosek you can make that work. That contract would have been movable when it needed to be moved.
Severson was never going to be able to stay, and I wouldn't have wanted him at what was being offered.
I just don't think you can lose that much of your defensive unit whilst downgrading the quality of player replacing them not to expect a decline in performance.