I would like to add Fagan into the bunch. He rose to generalship after I guess a fairly decent performance as a regimental commander at Shiloh and acting brigade commander at Farmington. He appears to have followed orders at Helena and attacked with his brigade at daylight as required but of course due to terrain and lack of coordination of other brigades was eventually repulsed at Battery D after his troops made a valiant effort. After becoming Major General and getting his cavalry division, I would say his performance was intermittent at best. I am not sure where he was during the Mt Elba fiasco and capture of wagons at Longview when Crawford took a brigade to Mt Elba along with Dockery. All the actions around Moscow Prairie and Poison SPrings really didn't show anything really outstanding on his part. Then Marks Mill seemed to be a positive effort on his part, except it did not proceed on his left as well until Shelby came thundering down the road and the trap was then sprung. It was a good plan that worked, but there was some difficulties on the left where the troops under Cabell etc had some issues early. After that though, the Jenkins Ferry campaign (where he had the ultimate opportunity to have been the hero and possibly played the key role in the destruction of Steele's force) did not give him any accolades and then the Missouri Raid did nothing to add to his ability. Col Wright even mentions this in his memoir when Fagan was begging Cabell to allow him to reform his dismounted troops and attack the works at Pilot Knob after a severe repulse of his men. As with many, it seems he felt his reputation and honor were at stake after this repulse and then all the issues in the rest of the raid. After that, he really doesn't show up much anymore. Then add to the fact that after the war, he jumped ship with all of his best friends, to include COL William Crawford his best compadre all during the war, when he accepted a generalship from Gov Brooks when all of his best officers were on the side of Gov BAxter during the Brooks-Baxter War.
I guess my opinion would be that while Fagan had some ability as regimental and brigade command, like so many others he was advanced beyond his capability due to his "political" friendships with others higher up than himself. He evidently knew how to politic and got those higher commands.