well, to tell you the truth, trying to support in a game without jungler, most times means its a low game, and your AD wont be even able to carry
In this case i wouldnt even play taric ,atleast the way fortuna/noble say for now
First of all, find a sunergy with your mate at bot. So he knows when you are going in, to follow.
Taric can burst down a target to 50% hp by his own without items, if he follows you dominate the lane
About the build, i would recommend Aegis of protection, Shurelias and a Frozen Heart. You could also build some AP(Deathfire grasp, abysall scepter if ur team needs it)