My guess is that Heath wasn't starting last season because of his tackling and his struggles with assignments. Church was limited in coverage, but tackled much better and wasn't missing assignments.
My guess is that the team figured that while Heath had his own deficiencies they believed he had more range and a better nose for the ball and while we could give up more yards, we could get more interceptions with Heath. And since our offense is productive and tends to win the time of possession, it makes for a net positive.
Problem is that we are not getting more interceptions with Heath. So just from that, we've got a problem. But add missing assignments and just some awful tackling I think we need to seriously consider a change of putting Woods in.
YR