When we walked in 2013 it rained quite a bit and I found my water resistant pants worked better than I thought they would - I don't see a need to bring rain pants next time around. I also wore a poncho so I was pretty well covered. Wearing a baseball cap under your poncho or jacket hood helps keep the visor of the hood up and keep your glasses dry. Since I used a poncho I wonder how wet the straps on backpacks get for people who wear jackets.
All the albergues we stayed in kept a good supply of newspapers for stuffing our wet boots at the end of the day.
Even though we also had an umbrella it was too windy most days but we did use it at the end of the day walking around in the rain. The idea in having the umbrella was that it would also serve as shade but we never got that far. We did see a few pilgrims with umbrellas but not many.