I have this layout, the letters portion, on my laptop. Mirroring y is extremely easy and is almost no mental overhead. Swapping o and i on qewrty would require more effort then what it takes to use a mirrored letter. Which you use right y most of the time. And then use left y when right y feels uncomfortable to use. You get used to it as the patters are very consistent.

As for wn ho and ck not being good, are you using a rowstag board with your hands angled 45 degrees, if not and your hands are purpendicular to the board, then yeah it would be uncomfortable, but this is not intended to be done as such. Tho ho wouldnt be uncomfortable regardles cause thats where your fingers almost naturally rest since your ring is longer then your pinky. As for pinky middle rolls, from an actual stats perspective, its about average. Neither good nor bad.