Three hours before is not unreasonable. Assume they're going to stop at at least one other resort to pick people up, and the busses won't go as fast as a vehicle.
There is no way I would chance getting picked up from my Disney resort two hours before the flight, even 2:30 would be my drop dead minimum, probably 2:45. What's traffic doing? How long is the check in line? How long is the security line?
Of course, I personally don't mind sitting at the gate, even for an hour or more. I'd rather wait for an hour than show up a minute after the close the doors.