I consider myself casual, leaning towards spending too much time in game.
Difficulty is set to a decent level.
Haven't completed the extremes yet, or Turn 5.
Got a Garuda Extreme the other day when I wanted to learn the fight... Before starting, everyone was talking about it as if they knew how to do it, but as soon as it started it was obvious they either had no clue, or had been carried previously, and rather than stay and admit they didn't really know the fight, they ran away on first death...

Anyone that wants more of a challenge than the game provides them can make up their own challenges... Like the Scholar that solo'd AK, Copperbell HM, etc. Do it for the challenge, not for any reward.