I don't think it is good for the quilting to overpower the pieced design. Rather the quilting should enhance and compliment the pieced design. Wholecloth quilting on the other hand is a showcase for the quilting itself and the quilting IS the focal point.
I have seen some quilts at shows where I felt like the quilting would have been better suited to wholecloth rather than a pieced quilt.
On the other hand, especially on this board, I have seen some absolutely gorgeous quilts with exquisite quilting that enhanced the pieced quilt way beyond what it was initially.
So, yes, I do think the quilting can 'make or break' the quilt. And sometimes it can be too much of a good thing. But when the balance is there it is totally awesome.