I have to believe you had a pre-existing problem with the input (drive) pinion bearings. I have done a lot of work with differentials and fluid development for same and if the preload setup isn't correct, you will have wear problems no matter the fluid. So I don't think the fluid base oil or formulation is/was your problem.
In developing gear lubes and working with transmissions and differentials, I have even gone so far as to have the metallurgy of the bearings/races dissected in a materials testing laboratory to determine cause and effect.
In one instance, a fluid I had developed for a racing event was thought to have caused or help cause a failure. The input pinion bearings (Input pinion to delineate from the differential pinions) has failed during a racing circle track event on a very hot day.
The bearings, races, input pinion bearings, etc were scored and flaked; all kinds of metal debris that had wound up in the fluid were taken to the metallurgical lab.
Two weeks later the report came back. The alloy content and hardness of the races, ball and roller bearings were analyzed along with the ring gear, etc.
One finding was the alloy mix was consistent with these types of bearings as compared to a databse of national standards and other, comparable bearings.
What was not correct, however, was the heat treatment of the races. The lab had done Brinell hardness tests of the races and found them to be too soft. Scanning electron microscopic analysis of the surfaces of the races from dissection cuts showed our fluid had laid down the correct ratio and thickness of EP additives.
So when someone tells me our fluid has caused their diffy or tranny to fail, I ask then to send me the parts and a sample of fluid, and I have them analyzed down to the um surface.
I am not saying this was your situation, I am just saying there is more than fluid to consider when examining failure modes.
