This is completely unacceptable! Gotta love "made in the USA" products...
I'd call Nick and Anthony at DT again and explain to them they need to step up, address their obvious poor quality control and take care of you. They've made more than enough money from the Titan community and need to exercise customer service now! Having YOU call repeatedly to follow up and then listen to Nick's lip service and song and dance wouldn't cut it for me. He needs to follow up with you when he's got real answers and 24hrs should more than enough. I'd make them send you a new pair using the correct part # along with a UPS call tag to send the defective ones back.
I'd make sure to post your issue on as many automotive forums as you can and watch their sales go north. Tell them you're going to do it to.
As far as I know their is no difference in port design between the Titan and QX56, so that excuse isn't gonna work. Looks to me like some lazy SOB just didn't do their job and either used the wrong flange or didn't check their tooling to ensure it was calibrated correctly before the CNC started. If the design changed that drastically between the Titan and the QX56, then the Nismo's wouldn't fit the QX and neither would the Stillen's. If he's talking about the 2011 QX56, their one size fits all approach obviously isn't gonna work and they need to have 2 separate part #'s. Either way it's their fault and they need to fix it.
Scratch Doug Thorley off your list boys and girls!!!