^^^ You're absolutely right-- I don't know if he can do better than Sarah. I've only got what he's offered in the McQ line, and quality and cut aside, the designs are rather watered-down separates gathered from any collection. And that's what I'm going by... and I much, much, much prefer Sarah's take on McQueen.
I don't expect any diffusion line to be as exact and precise as their mainline. However, there should never an excuse for sloppy cuts and ill-fits, which the McQ line has been plagued with. Diffusion lines aren't exactly bargains, as they heavily on the mainline's image to push sales at inflated prices, rather than quality of materials and masterful cuts. I can't recall the exact season, it was the one with all the autumn leaves on the runway, and you could clearly see the puckering, uneven seams and snags on the coats and jackets-- just dreadful