Having spent a fair bit of time playing other ARPGs and coming back to GD every so often, I have started thinking that single-affix Rare gear (not MIs, nor double rares) drops too often. So often that they do not feel special, nor deserving of their name. This is my experience of the main campaign. I do make a point of clearing almost all monster totems, which seem to be the worst offenders for showering players with greens.
I personally would prefer the greens to be less common. In exchange the double rare chance would be raised to stay the same, iron earnt from selling gear or as drops from chests and enemies could be raised to compensate loss. This would make rare gear feel more rare, more exciting to find and at the same time reduce the amount of time spent on the vendor screen.