I ****ing feel your pain. Alistar is so incredibly fun and game breakingly strong with competent teammates backing him. But he's nearly completely useless with disorganized baddies.
It reminds me of a game I played. I was Alistar, and I had a Twitch on my team, who was the only one on the entire team besides me who knew what the hell he was doing. After a certain point, after many repeated losses trying to work with the "group," we said "**** our team" and by god we dragged this noob ass scrubby bunch of losers screaming and kicking to victory. We literally 2v4ed at several points at windmill while they were being collectively kited to death by a Kog guarding another point.
My only suggestion if you plan to play a supportish character anyway, is to find the most competent player on your team, and you guys duo it out in every endeavor, just hoping the rest of your team will do SOMETHING useful. But I do know how really hard that can be.