This is probably due to shuffling everything around during the merger - they might be rotating aircraft in and out of different hubs now and adjusting their whole schedule to align with CO's. Have you searched for flights through EWR? There should be an early morning departure and high frequency to LAX from there.
EWR is just not a viable option for anyone on business who needs some semblance of reliability. Even the early morning flights from PIT can get backed up because of issues the previous day. (You hear that UA/CO? we're not going to rely on EWR as a connecting hub! Keep IAD viable!)
IAH might work better, there is usually a 6am-ish departure out of PIT, although it's a 3 hour trip down and then another 3+ to LAX, so travel time still gets stretched out more then a stop in CLE or ORD.