You can still knock people out of his ult so they can't get it a la Trist, Gragas, Alistair, etc. You can CC them in place so they can't move a la Morg, Annie, Zyra, etc.
I've personally not seen a tower dive work well at lvl 6 because once someone sees the ult charging they generally run and at lvl 6 a tower isn't going down in 2.5 seconds even with a fed jinx. When he ults against me I walk back, morg q the adc so they can't get free hits on the tower and reengage under tower when the ult is off. It's 2.5 seconds. If they stay under tower for 2 seconds of that and then leave, they will probably still take a turret shot. If they dive with minions then I just hit them for what I can and let my adc try and farm under turret. Ult is blown on a bad dive that got nothing but a little turret damage.
Taric is hardly as overloaded as people say. He needs CDR to really get his stun out often, his heals are weak until about lvl 7 or 8 AND they don't do much when spammed with the 1 stack. After all those factors are taken in, he gets gated by mana pretty hard pretty early.