I pretty much agree with you on all counts LB.
I haven't heard Justin Bradley's Arthur, because again, my PBS never even aired Season 6 until PBS's kids programming adopted that whole "PBS Kids GO" format, which began in 2005 or so, so by then, the Mark Rendall dubs were in place.
The second half of Season 12, Arthur's voice kind of went back and forth between sounding closer to Mark's Arthur, while still sounding too high-pitched and more like D.W. at times.
So far, Drew is the better Arthur we've had in a long time.