Regarding DECs suitability.
Just to clarify, my generalization refers to captains that have been trained in normal, well-renowned flying organizations and as such have had their command aptitude put to the test.
Naturally guys from less than desirable backgrounds should not make the cut, and maybe that's where airlines fail in the selection procedures. I maintain the notion that experience in normal airline operations counts in the left seat, and that's why DECs are here to stay.