First of all Taric hasn't been nerfed. I see it as a huge buff.
Try this build and be amazed.

Welcome to the pre-season build of Support Taric.

Here I will try and explain (the best I can) how I build and use Taric.
I see alot of people claiming Taric has been nerfed but imho he has been (outrageously) buffed.

For runes I use the standard Armor, Magic Resist, Health, and gold quints.
This will let you take a couple of hits early game without having to recall or turret camp.

The gold quints are optional but I like a steady goldflow on my supports.
+Stacks nicely with Ancient Coin

Utility masteries for gold, movement speed, faster leveling and overall better support.

Tank masteries for that little bit of extra armor and health. So you can sustain more damage early game.

Ancient Coin = Optional, I just prefer this Support item.

Mobility Boots = Optional, I help in other lanes as well so the faster I get there the better, also boosts survivability.

Iceborn Gauntlet = Spellblade + Gemcraft stacks lovely, and armor for better sustain.

Spirit Visage = This will keep your heal strong mid - late game, and magic resist for better sustain.

Locket of the Iron Solari = Armor, Magic Resist, Aura for support and an active for team fights or saving yourself or other allies.

Ruby Sightstone = Health boost, and lifetime supply of wards. ;)

First skill should always be your stun so you can help your adc get those early kills or stop their adc from farming.

From there on out I lvl my heal and armor skill. (and ofcourse ulti when available)

Stun is the last thing to upgrade because I rather keep my allies alive than stunning a little longer with a little extra dmg.

Exhaust = For a good slow, dmg reduction, kill secure, saving your adc.

Flash = Survivability, Jukes, Landing a stun.

Pro
Good Stun
Tanky
Good early - late game

Cons
Not much room for aura items

You can help your jungler secure red buff or dragon if needed.
Always ward dragon.

Do not be afraid to use every skill you have on Taric because your spells recharge so fast.
In Team fights you can use your ulti together with Locket of the Iron Solari to boost everyone.

Taric's heal heals way more when you use it on yourself wich makes for a good Tower Tank.

Ask your adc if you can help him get those last hits if not harass their adc by stunning and agressive play.

This is my first guide, if you want better explanations or if it needs to be expanded or if I'm just wrong please feel free to comment and help me improve.