The AE flow-ups that were forced on AA by the arbitrators decision generally had a tough time in training, despite helpful, fair and honest instruction. A lot of those guys have very narrow experience (50 seat RJs at best) and no big airplane experience and were having trouble with even the MD-80 and 737 school (none have gone thru the 757/767 program which is much more difficult). Many had lots of additional training required. Failure rate is about 10% from what I hear, at least so far. That seems to be much higher than traditional off-the-street hiring, but off-the-streeters usually have more breadth of experience in a wider range of larger and more complex aircraft than commuter pilots.
But keep in mind that the sample size so far is fairly small, so statistically it's not definitive.
Who is AA hiring, that aren't commuter pilots, but fly larger and more complex aircraft? AE has 70 seats right?