I personally dislike this build for a few reasons, and ill tell you why. First of all, AP taric is hugely unviable because of the ridiculous cooldowns of his skills. i mean, yes it scales well, but you are a support and as such you are risking yourself for that little combo every 16 seconds. definitely not ideal. AP taric also wastes his ult, which is what makes him viable in the first place. Using dps taric or aura taric is more effective because you can have a shorter heal cooldown / help out your team more, respectively. also, taric isnt THAT slow, and ghost is more viable. along with clarity. gives him incredible lane presence cuz he never has to go back. as for your explanation, your rune explanation doesnt even explain runes. And I'm sorry, but taric just is not a tank. people focus him no matter how tanky he is because of his ult, and as a result he should be more support and stay farther back in team fights so his team doesnt lose fights. now, granted this is an ap build, its not bad for an ap build. but your written guide is lackluster and not well thought out. Didn't vote down, but consider revisions please. =D

Now this build of yours is somewhat useful, since it boosts his heal a lot and also his abilitites damage and since taric can tank quite some damage, the lack of defensive itens isnt much of a problem.
Also put in a 6th item since theres just 5.
Good healing and decent magic damge build. +1