Pinning the Dock to a Corner in Yosemite/El Capitan
I filed bug #18701500 on this problem with http://bugreporter.apple.com/  

My bug was closed by Apple Engineering as a duplicate of bug #16814560, which is still marked as open.

Although Apple does not permit public viewing of the bug database—I cannot see the details on the bug that they have closed it in favor of—and thus you cannot verify my statements, this is proof to me that there is currently no solution to this problem.