I've had to search a bit myself when I was curious about this some time ago, and here's what I found: damage reduction from resistances is 1% per 660 points, so the 6k from major resolve gives about 9% damage reduction. But major protection is calculated after resistances have been factored in. So if for example you have 25% damage reduction from armor, major protection would shave 10% off the remaining 75%, giving you a net 7.5% reduction. Basically major protection would be about as strong as major resolve if you only had 6600 resistance, and gets worse as you gain more.
I did get this info from older forum posts, not from testing or checking the damage formulas, so somebody please correct me if this is outdated or even just wrong.