In my opinion the key area to be investigated is how micro-pits came to be created on the outer raceway. Was it corrosion due to moisture? Was it indentation from fine (or not so fine) metallic particles suspended in the lubricant? Was it a failure of the lubricant to provide or maintain an elastohydrodynamic film between roller and raceway? Was it related to long-term storage rather than operation?
How many different lubricants are approved for this gearbox?
Perception of "better" is open to interpretation.
From the same manufacturer an example is on some (not all) of the AS350 series you have the option of using a range of mineral and synthetic oils.
All are "approved" yet in this particular case experience dictates that the use of mineral oil will get you much better service life from gearbox components come overhaul.
The difference in the lubricant and their characteristics do have significant effect on all the points that Concentric quotes.
In years past many manufacturers used turbine oils in their main gearboxes. Mostly that has all changed as it worked but not that well in hindsight.
There are much better options available today. More common these days are synthetic industrial or agricultural lubricants and in a lot of cases automatic transmission fluids.