Taric's heal is garbage and his mana costs are too high
I've seen the title of this post so many times in just the past couple of weeks and it really annoys me how many people think this is the case. He has mana costs for a reason and would be broken for people who can use him effectively already if they buffed his mana. Here is a clip from my last game that shows how powerful of a tool his heal is when used on 4 charges with a bit of scaling (ap or heal/shield power). This is a very extreme case in a game against 3 tanks when I was highly fed, but the same idea translates to all games on him. If you actually build mana and make correct use of his passive, Taric is a strong champion.
https://www.youtube.com/watch?v=M90qg5_crnY&feature=youtu.be