It is a bit jarring how long they're lasting. Riko, particularly, feels like she's only being used as a way to keep Yumeji/Merry and John/Engi separated, with the upperhand constantly shifting between Riko and John/Engi.
I do appreciate that they are basically the penultimate bosses of the series I think, so it makes sense that they'd be tough to beat. My problem lies more in the constant shifting between "Riko is overwhelmingly powerful" and "Engi and John are cool as fuck", cause neither gets enough time to shine cause it lasts for so little. Like in this chapter, we see Engi decimate the Myconid Riko makes in a single hit, with Riko even saying she made it with the intention of it being sturdy, but then almost immediately after Engi gets to be cool, Riko smacks her and John's faces together and gets to look even stronger.
But I will say, as someone who isn't completely caught up to the raws, I'm pretty excited to see how Ushiki handles their defeats precisely because it's taking so long.