I think Alistar top counters Singed very well. All he has to do is heal his minions when the poison gets them low. This is gonna waste Singed's mana early game and make Singed commit to pushing the lane hard. Once he's pushed in he headbutts Singed into the turret, then pulverizes. It might not kill him but it harasses him enough to keep him low for a gank top. Alistar's ultimate keeps him pretty safe from turret dives from Singed on the gank too, which we all know he thrives on.
Thoughts? Comments? Criticisms?