I think safety is a tough position to evaluate because they are usually the last line of defense and covering for a breakdown elsewhere. Also, unless you have all-22 access you might not be able to see where they are lined up.
That said, Burnett has missed a lot of tackles and I sometimes got the impression that he was playing hesitant. Having someone like Hyde or HHCD should be an upgrade to Jennings/McMillian and I think it will be reflected this year. Getting an improved pass rush will make a big difference too.