It’s evident you’ve drank the Amsoil Koolaid

My question is did you ever give another brand of oil a chance ? My thinking is any good synthetic oil is going to perform the same. IMO , let’s say T6 Rotella would of done equally as well .
T6 15w-40 is advertised as a synthetic blend, so IMO that doesn't qualify as a synthetic oil. I also can't find published specs on HTHS or Noack Volatility, which makes me suspect.
The Amsoil DME I run is also quite a bit thicker at 100°C than T6 15w-40 (15.6 vs 14.7), which I consider a good thing for heavy use.
When Amsoil DME came out I switched to it from AME that had a 100°C viscosity of 15.0. That .6 increase gained a little pressure and lost a little temperature when towing hard, those are both good things. That was with aftermarket pressure and temperature gauges on my 05.
Modern engines run the oil hot, don't trust the BS oil temp gauge on the dash, and you want thick oil to be able to handle that.
Sure T6 may provide great results, but I don't have to try it to know I don't want to run it...just like I don't have to buy a DMAX or Powerjoke to know I don't want to try one.
One of the reasons I like to run a full synthetic 15w-40 is they generally have a lower Noack %loss, around 1/2, of a 5w-40 full synthetic... which goes back to how hot oil can run on modern engines.
All in all we're pretty lucky with these motors. Very few oil related issues, and pretty good OEM OCI's... go look at a 6.7 Powerstroke's OCI if you want to see how bad it can be.
I decided to swap this truck from the T5 and Cummins filter from walmart to the Amsoil as I am paying to be a preferred customer it only cost me 127$
Take a look at the DBL7349 from Donaldson. It has the same media as the EaO-80, but it's a bit cheaper. I get dealer pricing on Amsoil stuff and use the Donladson.