To be fair though, that's a fair amount of paying attention they're asking new players to do at that level.
Heck, when I was in Quarn for the first time I barely understood my class and just trying to perform basic combos took up a lot of my attention.
I kept dying to that miniboss because when the platform would light up, either it wouldn't be onscreen or I'd be watching something else and not notice it.
When the bees came up, I wouldn't even see them cast final sting and I was really confused why I kept dying.

No, the mechanics aren't hard, but every part of Quarn hits new players with multiple new mechanics, which can be tough if the player is still getting their feet under them.
If everything is still new it's hard to parse a barrage of new info.