Alistar is one of the least rewarding champions in the game.

With a winrate fluctuating between 45%-48%, that alone should tell you something. His signature move headbutt, the reason to pick Alistar and the bulk of his power is not even special. Vayne can do the same thing on a shorter cooldown with a longer stun with higher base damage with AD scaling at a range. He has a weak laning phase AND weak teamfighting. With fairly long cooldowns, bad AP ratios, and an ultimate that brings absolutely nothing to a teamfight.

Build him tanky and he does almost nothing. He stands there and watches his teammates die as he waits for his cooldowns. Build him AP and he's squishy but still very very weak. An AD build is viable simply because the other builds are just as weak. To peel correctly in teamfights without headbutting priority targets away requires very good positioning and no matter how good you are, sometimes you just can't pull it up.

Please give him something. Overall his kit probably has the least synergy in the game. His heal is pathetically weak and saps his mana in a few casts. His ult is his biggest issue. The best way to counter Alistar is to just ignore him. Why give a tank/support an AD steroid that he can't even make good use of?

The only reason to use him right now is to babysit vayne until she's a monster but then you've got a hypercarry and a useless support come lategame. If he is given a buff to his heal or ult, his other 2 abilities are perfectly fine, he just needs SOMETHING. ANYTHING.

tl;dr suggestions: *Make him a half decent jungler again. Buff his passive to deal extra damage to neutral monsters. Buff his heal to be more potent when he's alone. *Reduce mana costs or increase AP scaling. *Rework his ultimate entirely.