I have conflicting opinons.
Firstly, I think what women wear is up to them.
But contrastingly, I think that in the work place, a uniform standard should be applied to both men and women. I don't want to see anyone's underwear while I'm at work (thin tops for women, low rise trouers with pants above for men).
Finally, I've been both big boobed and small boobed (post breast cancer). Those saying it is hard to cover big boobs are right. A non low cut shirt on me with my previously large boobs was revealing. Now, with smaller boobs, the same shirt is very modest. The only way for big boobed women to avoid this is to add an extra layer underneath, with a camisole.