Something tells me (im guessing) that you have only tried T6. I too had quick to sheer tendencies with T6. I currently use T4 and it seems to hold up great. I dont really check on the JASO certs anymore on diesel oil.
What makes it good for MC use is still there with or without the JASO cert. I've been using T4 for years and years on my old Honda XR650R and its running better then ever.
Nope, I've tried them all. T4, T5, T6, and numerous other brands of HDEO oils.
I do use T4 in the Diesel Dually. It would be great if a cheap, and readily available HDEO worked to my satisfaction in the sportbikes.