We have an Assassin Support (Pyke) and an ADC support (Senna) now. Juggernaut Support wen?
Think about it. A big wall of stats that scales off levels and builds defensively, add in the threat of his/her sheer stats overwhelming you if you try to all-in on them. Works great with either farming ADCs who would normally be more afraid of an all-in by big kill lanes (since going balls deep against a Juggernaut is just asking to get wrecked), or alongside harassment queens like 
to turn a normal lane into a lose-lose scenario. Stay at a distance, you lose. Go for the big play? You lose.
?
???
Taric already fits the bill, at least sometimes. Old Taric certainly did. If you disrespected him even a little, he would smash you like glass and drag your team through the shards you leave behind.
Works as a support especially into engage/melee supports (Leona, Blitz, Naut). Although I treat him more as a counter pick, wouldn't recommend picking him blind. Personally, I played him support only twice or thrice across my accounts though, cause by the time I see I am into a good matchup, he's most of the time already picked or banned from the start. But yes, paired with high early high damage adcs, as long as you land your e you are guaranteed a kill. And with late gamish adcs, you make up for their lack of early damage pretty well.
