Decent guide, and I do agree that the coin start is better for early-game sustain and late-game gold.

My only grudge against the 0/15/15 on Taric is that Greed gives 90 gold per 10 minutes and Scavenger gives 126 gold per 10 minutes, so by 10 minutes you get 216+40 and by 20 minutes you get 432+40 assuming you were within range of every minion death. Realistically you'd get closer to 300 gold by the 20 minute mark.

By contrast, Legendary Guardian gives you +4 armor and +2 MR. We know that each point of armor or MR is worth roughly 20 gold (from the 300:15 ratio on Cloth Armor or 400:20 ratio on Null-Magic), so Legendary Guardian gives you 120 gold worth of defensive stats for each nearby enemy. That's a persistent 240 gold of defensive stats in 2v2 laning, and 600 gold of armor in 5v5 teamfights. You're also missing out on 60 gold of early-game stats from having only 2 points in Hardiness and Resistance.

Also, how would Taric solo baron? He'd have a tough time with Dragon.

There are many factors with the Relic Shield.
Relic shield only makes you money when you last hit creeps. Late game your allies will wave clear too fast for you to get your charges off. You will also be roaming out of lane to ward and support so you won't get money if you are out of lane unlike Nomad's Medallion. It's a slow start and Taric really needs Mana Regen early game unless you plan on buying mana pots or backing often. You must spend the gold on the targon's brace to get the full money effect leaving you without your Sightstone and boots. Near endgame Face of the Mountain's Active can come into use if you build a lot of HP, but the damage radius from the AoE seems so small it doesn't hit anything if you end up shielding ranged champions. Talisman of Ascension Has better CDR. Mana and HP regen. It's active is for the full team to escape or push. I find the Relic shield lacking IMO. This doesn't stop you from using it, it is just my view on it. This guide is meant to "guide" you on what to build when and why, not necessarily what is "best".

@emoriam
I personally don't like Bandit on Taric since the gold gain is only on kill or assist is 15. Generally if your total is say... 2Kills / XDeaths / 8Assists = 150gold. If you wanted to make more gold it would be better to take atleast two Greater Quintessence of Gold which makes you 240 gold at the 20 minute mark and throw that extra point into something else such as Recovery or Perseverance. Otherwise thank you for pointing out Strength of Spirit . I completely looked over that.

please explain why you don't buy relic shield. also masteries are funky. 0/14/16 is the way to go imo. or say f it to the utility and go 9/21/0.

Warmog's Armor and Guardian Angel are doubtful choices but I guess no one really knows how far supports can currently expand their item builds due to the factual changes.
For Masteries what about going less tanky but optimized 0/13/17 like this: http://i.imgur.com/xgJPWJh.png (I thought of Strength of Spirit because you chose items which provide a huge amount of extra mana)?