I think the quints are a waste. Is that 3 gold / 10 sec with all of them? That's only 18 gold a minute. I'd much rather have virtually anything other quint.
Exhaust seems less than ideal on Taric. You have good CC already. personally I'd rather have ghost, flash or cv.
You should drop greed and get the mastery for clarity. Greed is pretty worthless as a mastery but improved clarity is diamonds on support champs. Taking good hands mastery when you're stacking snowball items is... strange. On one hand you're planning on dieing and on the other, you're not. I'd put those points into Perseverance first.
The skill order seems odd to me. Why are you maxxing Dazzle first? The stun length doesn't increase just damage and the cooldown is reduced. The other skills are more important. I much prefer 1 point in dazzle at one, then go Radiance > Shatter > Imbue. Dazzle gets brought up last. Dump more points into imbue earlier if you find you need to heal a lot.
The item build is curious. It could work on Taric as you're tough for a support champ but with this build you're playing more as a tank I guess? Isn't mana regen a major issue early game? I don't feel like I can do my job with taric without taking a mana regen item first. Three snowballs plus Taric's utility should get you focused every time but you have a very small mana pool to run your ult with and you have no mitigation beyond shatter. I would think focus fire would still take you out relatively easily and you've given them every reason in the world to focus you.
Plus with him having a built in aura from shatter it just kind of makes sense to stack more auras on him. I approve of your Aegis but I personally try to add at least one more aura in the form of Stark's or Sould Shroud depending on what my team needs. It's also fun to get offensive with your auras and get abysal or frozen heard.
That's definitely not my Taric play style but if it works for your buddy, more power to him.