certainly is tanky, and i'm glad you have good success with it. i would be interested in actually seeing your playstyle ingame, because i just want to gauge my eyes out, not having the CDR or mana regen i'm accustomed to. But thats just me, i do not believing in nocking any build that works for its user, so gratz! ; P
However, on worst items ever for Alistar, i would put warmogs -he farms too slow & has way too few kills to make it a wise investment, & give frozen Mallet a lot more credit. Why? Because of presence. If a team wants to ignore alistar between cd's fine, but if you want them to feel obligated to engage Alistar, frozen mallet does the job. Lets see how their squishy/fleeing members fare at ignoring His Tankiness when all he has to do inbetween CDs is auto attack, slowing them evey hit so your team mate can finish them off or you can simply bludgeon them to death. Like you said, its not about the damage, its about doing what comes natural to Alistar. Alistar has long cd's esp if you dont max his cdr, he is naturally tanky, & what can be more natural to any champ than auto-attack? so lets see... Frozen Mallet enhances his tankiness (+700 health), gives him battle presence between his cds, compensates in a way for his natural slowness by slowing his target, & doesn't need high AD or AS to be effective. Sounds like it fits Alistar pretty darn natural if you ask me! ; P but that said, while i think frozen Mallet is great on Ali, i would relegate it to slot 5 or 6... it is not at the core of his build.
Anyway, very nice guide, & engaging. It made me think deeper about how alistar works, & i appreciate that because Ali is my man! Aint no other man but hIm!!! ; P