What of Heath have you seen lately that pained you when he was on the field?
I think he played well last year in a limited role and at least the last half of 2015. However, his responsibilities in that role were different than the starting safeties. He was primarily playing a deep zone, while Church, whom he would be replacing, played a lot of short zone/run defense.
If we run a true two-deep, Heath may be fine as the starter. I don't know who he will handle Cover 1 or even Cover 3. Or how he'll handle being the only deep safety if Byron covers the tight end 1-on-1 in the base, although I believe I saw him in the role some.
There's a big difference in being one of five or six DBs on the field and one of four.