This discussion has largely missed a major point:
You're going to get wet riding in the rain, it doesn't matter what you're wearing. Waterproof/ resistant fabrics (even if they claim to be breathable) won't breath to the extent that your body emits moisture during exercise. Furthermore, water will find ways to seep in: you're on a bike. The key, in my book, is staying warm, not dry.
I rode the divide way back in the day and carried full gortex rain gear and neopreme booties: my first foray into wilderness travel. I've learned a good deal over the years, and fabrics have changed. My set-up would now be much different!
My feet get cold riding in the rain even on a warm summer day, booties rectify this issue. A shell jacket with a hood (sil nylon or precip style jacket) and perhaps pants. Hood is best under the helmet. Pants (of same material) are optional. Look into these materials because they are lighter and less bulky. And weight is a consideration: extra gear will slow you down, you don't need it! You could easily ride the GDR with 15 lbs or less of base weight gear, a Bob of course, would double this as the trailer itself weighs 14 lbs.
An ibex, icebreaker, or smartwool long sleeve shirt will help keep you warm if you intend to ride in the rain. While synthetic fibers are hydrophobic and wick, wool is one of the only materials that retains loft has insulating properties when it's soaked.
pm me and I'll give you my phone number if you'd like to have a chat concerning this stuff..