I guess the posts form Dale W and Buck confirm that weather in NW US and Canada merits rain pants, even though I haven't needed them in Colorado and New England when backpacking.
In mid-May, I was on the Cohos Trail in northern NH for a week, with three days of extended rain. But here the extended rain fluctuates back and forth between light drizzle and heavy deluges, and there is usually some cover below tree line. The Marmot Rockstar soft shell pants I used never got anywhere near wetted out, let along sopped, and dried out completely in the tent each night. Usually, they were dry enough by bedtime, that I just wore them in the bag. Had the same experience with them last year. Hope the DWR holds up.
In response to Kat P's question about bringing a change of clothes, absolutely. In addition to the Patagonia baggies - extra briefs, a fleece top and cap, Cocoon PG Delta puffy top and bottom, 2 pair extra heavy coolmax sox and thinsulate booties stay dry in the clothes bag. These have saved my bacon often enough when the temperature plummeted at night after extended rain that I'm willing to carry that much weight. There have been some nights when it took all of it to sleep comfortably and warm in the sleeping bag. Not sure that this combination would work more than a week of extended rain without a break, but that would be pretty unusual for the NE or CO.
The ReviveX line is made by McNett, the same company that makes Seam-Grip sealer.
What I'm getting from this thread is that what you can leave behind to save weight depends on the region you are going to and the season. The recent increases in fluctuations in climate do make it more difficult to plan, however.