A few comments:
Yes, the case geometry of the 6.5/.284 contributes to throat erosion.
The majority of barrel erosion is caused by hot powder gas, and the effect naturally dissipates further from the case mouth--which anybody with a bore-scope will soon see. A longer neck protects more of the bore in front of the case.
Shoulder angle also has an effect: If it "funnels" the hot gas right around the mouth of the case (or a little in front), then the throat will erode quicker. This is exactly what the shoulder angle of the 6.5/.284 does. The shoulder/neck combination is even worse in the .243 Winchester.
Both of these effects have been demonstrated in considerable military research, undertaken because of a desire to make barrels last longer. They're also why a 6.5-06 barrel usually lasts longer than a 6.5/.284 barrel, and a 6.5-.270 should last a little longer yet--though the effect might be negated by what might be called the .270's "G-factor."
Another big factor is the powder itself. Double-based powders burn hotter, and very "progressive" double-based powders (which extend the burn further down the bore), tend to fry throats quicker. Which is part of the reason some very successful competitive shooters use single-based powders: They don't burn out throats as quickly, so an accurate barrel lasts longer.
