My 2012 is the 6.7 diesel, but it does not even drop from OD on slight grades. And it smoothly downshifts on greater grades, never skipping a gear. I don't think what you are experiencing would be normal even for a gasser.
I had an intermittent problem on a 2004 SD only while towing. So I hooked up an implement trailer with a tractor on it and went to the Ford dealer. He connected his portable diagnostic monitor and off we went. Problem showed up, he noted the problem, back to the dealer, replaced the EGR valve, back on the road within the hour. Maybe your service tech or manager would do the same.