That list aint completely right. There is no mid core. There is only super easy and super hard. Until a few years ago i was doing savage raids and extremes but for me it was to much stress for to little reward.
My Wife started playing like a year ago and while shes dying of boredom in normal dungeons, she would never dream of killing a current extreme primal.

So no. There is no midcore. For me personally, midcore would be extremes or Criterions without timelimit. Its always the "we devs make it easy for us" Timelimit. That is also the Reason everybody has to slot full DPS materia on every Job that exists.