I agree with you. I still believe Merino will keep you warmer when its wet than synthetics - but my experience over the past couple hunting seasons indicates if you arrive at your stand dry or have a thin synthetic that 'cooks' dry in short order, you'll stay warmer longer on stand than wearing a merino next to your skin and having it stay damp for a long time. The reason I'm looking into a dual base layer system is to keep all moisture significantly away from my skin. I tested that theory this fall with wearing a synthetic next to the skin and a thicker merino as a mid layer. If you sweat enough to get the merino damp, its seems like the same effect as having it next to your skin - you chill easier and quicker.
So, I'm waiting for Kuiu to have another sale to fully test the theory - Peleton 130 (thin, moisture wicking synthetic) next to skin, Peleton 200 next (thicker synthetic with moisture wicking properties), followed by fleece/merino sweater (Ice Breaker 320). Depending on temps, I'll hike in with that set up. I'll wear a Kuiu Guide jacket when I cool down a bit and still hunt or take a stand. I'll have a down or Primaloft puffy in my pack for extended sits. I think that system works for about 60-70% of my hunting in the east and west. For my eastern TS hunting, probably go with the same base layer setup and insulation layers. The outer layers will change according to the temps - everything from a Kuiu Peleton 240 to First Lite Sanctuary as an outer layer.
I guess the short version is - I'm switching back to synthetics next to my skin except for situations where I can remain sweat free. I still love merino next to my skin but don't like how long it takes to dry.
A big thanks goes to Form D for prompting and providing thoughts on this. It wasn't until I started paying attention to why I was getting cold over the past couple years and Form's thoughts that I connected the dots. I didn't have this problem when I wore synthetic or synthetic/merino blends under fleece. It wasn't until I switched to all merino that I started having issues. Interestingly I caught a Youtube by Jason Hairston explaining why Kuiu brought out the Peleton line. It seems the Kuiu crew was hunting (New Zealand?) and all the guides wore synthetics next to skin because merino stayed damp too long. My experience matches those statements/thoughts.
