I actually disagree. Yes, changes are definitely needed. Yes, Gase has made mistakes. But, this isn't a playoff team based on talent either. Changes should be made, but not wholesale changes. Not yet anyway.
I'd give Gase one more year with the ultimatum that he needs to find a new defensive coordinator, someone who has experience and has been successful. Grier's track record is actually pretty good. Tunsil, Howard, Drake, Godchaux, Taylor, Fitzpatrick and Baker were all brought in during his regime.
Give Gase one more year and if he can't get it done, then it's time to go. I honestly don't understand why Grier would be on the hot seat.