I have asked around, and as far as I've been told, we've done nothing about the availability of missions, or 'nerfed' them in any way, but this is what I learned:
There is a small change with the mission difficulty slider, though you will only notice that at extreme selections: Earlier - only the last pixel on the difficulty slider would give you the 'hell' missions. What we've done is increasing that area to cover more than that lone pixel, as it was often hard to 'hit'. This has shifted the disposition of the difficulties slightly. It does not change the settings in the 'middle area' (approx. 35-65%) in any way.
Anyway - this change only affects where you'll have to put the slider to get your desired selection of missions, not the content and nature of the missions themselves.
Umm, hope that was understandable...
So, what tool should I choose to punish that coder for not telling us?