EV's 252 HP / 128 Def / 128 SpD
Careful Nature (+SpD, -SpA)
Well this is something that I have been toying with for a while. This is the only set that can be utilized with Bronzor. His offensive stats are not worth putting any investment in so support set is the most reliable. Maxxing the HP stat for maximum bulk and mixing it's defencises makes it a good wall. Stleath Rock and Toxic are the most obvious choice for it. Trick Room helps out for your slower teamates, such as Gurdurr and Musharna. And Gyro Ball is there in case of taunt, but do not expect any serious damage to come from it.
Some good teamates would be Wartortle to resist any fire moves directed at Bronzor, and Musharna for the Trick Room support.