I too, was critical , initially of the small mini buses. Alan ( man at departure gate - ) was open to suggestions to improve it and a larger bus was suggested by many. However , the smaller minibuses actually staggered the pilot delivery to aircraft , thus staggering and minimising the queues at the holding point so possibly a bigger bus wasnt going to help.
Yes I can see that might well be the case and of course standing in the queue fuel is not being burnt....
As others have said though staggered departure slot times would be best.