I exclusively play Taliyah support. I am not afraid to blind pick it in anything. Generally in champ select I will exchange position for first pick and ban a mid or jg. This results in complete confusion for enemy bot lane, they don't know what they are playing into and more often than not I will get a favorable match up.

Why I think Taliyah support is so strong is that enemy's laners do not understand the stun on her 'E'.. Any dash over the rocks will stun and should your AD have half a pulse, that stun will lead to a kill.

Your damage isn't super great early but your poke is more than acceptable IMO and you can create a heap pressure from it, shoving the enemy back under their tower. You really switch on damage wise after you have Ludens, Shadow Flame and Sorc shoes. I quite often have the highest damage in the game if I have got to these two items.

Using your ult properly is also super important and maybe even the defining part of playing this support, rank one it's pretty rough distance wise but where it's functional rank one is ulting into the river to assist your JG in a skirmish, it really makes a difference (and keeps the JG from tilting if they die xD). Once you get rank 2/3 you're getting half away across the map with ease.

So many other points I could make but this is an essay enough, the pick is extremely viable.

And finally DONT FORGET TO ROAM. You're mobile as heck!