Suggesting that AA would willingly take a diversion is absurd. The costs for AA are huge - an extra cycle on the airplane, crew costs, dealing with misconnects at LGA, landing fees, extortionate fuel costs, etc.
On the other hand if AA were to hold all inbound LGA flights whenever there was a bit of weather in the area we would have pages of "OMG AA WOULDN'T TAKE OFF FROM XXX EVEN THOUGH IT WAS SUNNY IN LGA". ATC isn't going to let AA intentionally hold traffic back and then dump several hours of flights all at once so the most likely scenario would be just canceling the flight. I mean that's better than a 2.5hour delay, right?
I've had my share of diversions. During all the freak summer rain in Texas up through the middle of July I had no less than 6, all on DFW-IAH, IAH-DFW, or ORD-IAH segments. One of those 6 was actually a double - ORD-(sat)-(storm #2)-(back to aus)-IAH. My SO left DFW for LHR at about the same time and arrived DFW-LHR before I arrived ORD-IAH. That was super fun.