Originally Posted by Sumutherguy
Sheen is absolutely essential for Alistar when he's fighting in lane, adding about 57% increased damage over the course of his combo at level 5. When playing Alistar, his strength only halfway lies in his ability to tank. Equally important is the ease with which he can feed a dps lane partner kill after kill in the first ten minutes of the game, and Sheen is vital to such. It is also excellent later in the game for boosting up damage when one would otherwise be entirely ignored, as pure tank Alistars often are.
You get ignored regardless of whether u have sheen or not, and late game getting an extra 100 damage on 1 attack is not going to be a difference maker when everyone has their survivability items.
As I stated above try chalice and mp/5 runes. I max Headbutt first and spam it to harass the squishy in my lane until im ready to ghost or flash in to feed him to my lane partner. At worst you force them back or make them blow mana, summoner spells, or healing hurting their laning phase in general.
Trust me I used to run sheen but ever since they enforced the CD on it, it has become a poor choice to get. You used to be able to get three sheen procced hits in between your combo, now that's impossible.
The only time I grab sheen now is if I run a tower wrecking build with him.