I think that part of the problems stems from the fact that it was kinda-ish advertised as normal/ex from the onset?
I could be wrong but that was the general idea that I also got, but I knew they wanted to go for something more difficult on the 4-man scope so I wasn't really caught unaware.
Those who had that idea however, they stepped into it and were bombarded with it's Ex+ difficulty-- this is NOT comparable to normal.

With that said, like chizLemons pointed out there's already the EX trials that cover that middle ground pretty well in my opinion, and that is something that people should DEFINITELY go experience and try out BEFORE stepping into Criterion dungeons.

Had they went with their normal formula of: Variant = mega casual/exploration (love the content itself), Criterion = Normal/middle ground, then you'd have a Criterion = Ex, then a Criterion = Savage, not only would it be, in my opinion, a MASSIVE amount of wasted resources, how would it be any different from what we already have?
Criterion was meant to fulfill a very long requested niche of 4-man HARD content that doesn't hold punches, it's not meant to have a "middle ground" you know? Even if I understand what you're saying.
They might add a middle ground eventually but I don't really see it happening.

If we talk about the rewards, however... well that's another story, I'll leave that probably to another thread.

Right now with this added content in terms of difficulty from easiest to hardest:

- Normal
- Variant
- Ex trials
- Criterion
- Savage and Criterion savage (no point in saying X or Y is harder since it's a different party size)
- Ultimate
- SE getting their crap together and actually provide a proper reward structure by restructuring the current existing one.