Sounds like you have tried everything already, so it would be a hardware escalation: 1-800-821-2797 or 1-800-835-6100
I just did and that didn't fix it. We have 3 of these 6515dn units and they all print teal as blue, all other colors are correct. I guess it may just be a model defect.
Have you tried a color calibration?
For some reason, the Xerox WorkCentre 6515dn seems incapable of printing teal. Such as hex 579195 or CMYK 42, 3, 0, 42, any teal hue seems to print as a very blue color.