I wouldn't say no if criterion dungeons turned out to be FFXIV equivalent of WoW mythic+ dungeons with a difficulty set between extreme and savage or normal and extreme.
But seeing as they have already stated criterion dungeons will have four layers of difficulty, then maybe all the above are possible different layers of difficulty. The first layer being a normal difficulty as an introduction to the new content, with the second being somewhere between normal and extreme, the third being between extreme and savage, and the last layer being a savage difficulty dungeon.
I think that might satisfy players who like running content with fewer people and would prefer killing mobs and a bit of exploration around rather than fighting a boss in an arena.