So trying out Taric top and I got to say he is AMAZING against AD heavy teams. If you think your team can last to like 35 minutes then you can grab a tear as your first item for a muramana, otherwise I would say skip the whole thing if you think you need early game power.
You'll get over 300 armor easily and adding up all my damage before resists I was at something like 500-600 damage with muramana active on auto attacks without counting gauntlet procs. So against a team that is AD heavy you're going to be able to just run in and either protect your ADC by attacking the divers or go for theirs because they cant take you on so they're forced to either have their team focus on you or having the ADC only be able to hit you as they try to kite. Either way its a good situation considering you're going to be the tankiest person on your team and you make it easier for your ADC.
It's actually surprising how much damage Taric will get while still building tanky. However this is shutdown against AP heavy teams because you cant stack the armor/mana items without being blown up by AP damage and there aren't as many choices for MR/mana that fit Taric.