Uh, the first 3 on that list are starters--which are top notch.
The next 3 on your list? Webster was unimpressive IMO last season and is coming off an Achilles issue. I'd rather have the $3 mil to go towards Donald or extending an OL. Shields hasn't played in 2 years and, personally, I'm concerned about his noggin. So now we're down to Hill as next man up. Then who?
However, your point about Safety depth is well taken. I have been advocating drafting one because Joyner might be tough to sign next year and should he get hurt, we don't really have anybody who would inspire confidence.
Yes, let's discuss the next 3 on my list:
1. Shields - Former Pro Bowl CB who has had injury issues. That's not a problem when he's our #4 CB. He's depth.
2. Webster - You say he was unimpressive. I could not disagree more. He was a solid #2 CB last year, and the Vikings game is the perfect example of that. The durability concerns are accurate, but the fact is that he's our #5 CB. How many teams can say that their #5 CB is a solid #2 CB? Exactly.
3. Hill - He performed admirably in the playoffs against the Falcons. Many here thought he might be able to step into our #2 CB role. He's our #6 CB.
You're not going to have All Pros as your #4, #5, and #6 CBs. However, we have two guys who are arguably starting caliber CBs on at least a handful of NFL teams (Shields and Webster), and we have another guy who played well when thrust into the starting lineup last year. We're stacked at CB. We don't need starters or depth there.
And I see no point in cutting Webster. His contract ends after 2018. It has minimal impact on any extensions. As we learned last year, CB depth is invaluable. Keep him. You're not going to find someone better that's cheaper. And I'd rather spend our draft picks improving depth at our spots.