So I'm wondering if the big boys have so many does that they don't even pay attention to the calling and the decoys I've put out.
We had that problem in my neck of the woods a few years back. There were so many does that the bucks paid no attention to rattlin' antlers or to doe bleats. Since the ratio is now more even the bucks pay much more attention.
Have you considered a subordinate buck decoy instead of a doe decoy? That might pull some of the larger bucks in.