Mincey showed plenty of hustle and was a decent tackler. I think his shortcomings are no more than you'd expect from any college DE trying to make the transition to OLB in a 3-4 scheme.
By comparision, Pierre Woods had prior experience at Michigan playing OLB in 3-4 sets, he did a better job at edge containment and was as effective a pass rusher. He also showed a better understanding of pass coverage (even if horribly raw in that area), he also had more Special Teams experience and it showed.
Mincey could be brought back later in the season when there is a slot to spare for giving him OLB training time, or they need a pass rusher to simulate Dwight Freeney - I won't say he is gone until the season is over and the NFLE players have been allocated.