If it's going to be very wet I hang the camp bag with everything but my shelter in it from the loop inside the peak of my SL3. I have more and bigger trees than you do in my area that also work. With you on not expecting Cordura to keep much water out!
I'm also with you that I wouldn't feel the extra weight of the main bag of the EMR II, despite being much older and broken down than you are!

I'm kind of surprised that nobody has said I need to get in better shape so I can carry all that extra fabric, or that I should lose the weight from my body not my pack!
It's really not about the extra weight, though to most backpackers shedding 12 ounces from a pack would be pretty appealing. It's more about the high functionality and versatility of the bag when it's off the frame. And it's only two g-hooks to remount it and head out. It's the sweet spot for me for now.....
I try to avoid saying always and never because I keep trying new things and I might run into a scenario where a big bag skins the cat better for me. I tried the T1, T2, Highcamp, and I settled on the Nomad/Camp Bag combo at this point. Heck, I had a mostly empty 115 liter Lowe Alpine on my back when I bailed out of camp after a Dall Ram and I survived but the sheep didn't!