This past winter I attempted rooting a large number of cuttings from multiple sources using the same process for all of them (Jon's Uline bag method).  There was very limited variation in process.  In the end what I observed was that while some varieties may have rooted better than others, there was a greater distinction between batches from different sources and the apparent quality of the cuttings when received/started.  For example, I had some that came from one source that nearly all rooted.  Meanwhile I had a great number from another source that barely any rooted.  The later I was told had been hit by some cold weather shortly before taking the cuttings.  Visible damage on this later group wasn't overly noticeable, with a couple exceptions, but nearly all of them died with the exception of just one variety.  I think that variety may have been better suited for the weather since the parent tree has been long established in that local.

That said, my hypothesis is that the quality of the cutting can be one of the most important determinants of success.  What do you guys/gals think?

Yes, cutting quality certainly does significantly impact success.
However we need to determine what quality means.

Things like

Time of the year taken
What kind of cutting ( end or center cut)
Thickness
Days in storage
Storage temp, humidity
Treatment with fungicides
Variety

all need to be considered.

Also:
Exposure to frost
Overall vitality of parent tree when taken (including bad FMV)
Whether it's been stored/shipped in damp towel that led to molding
If ends are waxed, did the cutting get damaged by the heat
Number of nodes

What the ideal time of year to receive cutting. Are top cutting the best. Should the be unwaxed and,wrapped in plastic after cleaning of shipped bare ?

I receive cutting from one source i buy from that are good but always wrapped in wet papper towl then wrapped again in brown papper then days latter when i get them they are almost water logged. So i have to take them right out let them dry for a couple hours. then wrap in plastic and store. Its a pain and probably not good. BUt he has good varieties and they do root. Some people think it necessary to wet but its not in my opinion

I've received cuttings in all kinds of conditions. My least favorite is wrapped in wet paper towel. My favorite is wrapped in plastic wrap.
I store my cuttings in the fridge till March. This can be up to 4 months. Once you receive your cuttings you must inspect them and then re wrap them. If they look a little dried out I soak them in water to rehydrate and set them out to dry for a few hours before wrapping in plastic wrap. If they are wraped in wet paper towel it is wise to wash them off to clean off any mold that is either visible or not but has surely started. Dry and wrap. I waxed my ends last year, I have not this year. Hope this helps.