Although higher necks are not good for bigger busts, is there an exception?
You're right, low necklines are definitely a better option if you've got a bigger bust; they help to reduce the appearance of your bustline.
However, high necklines can also look great on women with big busts if they:
*accompany them with a reasonable-sized long pendant necklace that sits between the breasts - this looks great; or
*a scarf; or ...
*an open jacket, vest or cardi. Layering using different lines, textures and colours can work really well.
What you're trying to do is break up the visual area of the bustline. Whatever you do, don't add unnecessary bling, embellishments, frills or ruffles to this area because they will only accentuate the bust.