I think 2 little changes could make Taric the best freaking support ever:

1: Change his passive so that instead of dealing bonus dmg per hit, you recover mana per hit. Tarics biggest weakness is that his mana costs are just crippeling. And its not really a limitation needed to keep him balanced...

2: Make him ghostet while casting his E. Lets be honest here, the minion block in this game is TERRIBLE! I cant count how often i missed that important stun just because a minion in the same zip code just decided to have a block-box the size of Miss Fortunes Boobs...