I live in a part of the country (Pacific NW) where weather is hard to predict more than a day or two out (too much ocean out there). And if you're hiking in the Rockies you can usually assume afternoon thunderstorms, with cloudburst, wind, hail, even snow. I don't rely on weather forecasts to stay dry (bitter experience here!) and would never go out without good rain gear.

On the other hand, if it looks like a long dry spell ahead (contrary to prevailing myths, we do get them in Northwest summers), I may just pack a suit of Dri-Ducks, which are quite light, although not very durable, and hope never to have to wear them.

There are a number of lightweight rain gear options. Red Ledge Thunderlight (which I've found quite good) and Marmot Precip (which I haven't tried) are among them. Red Ledge is a bit easier on the budget (Campmor has them).

There have been many times when I've worn only the pants--it may stop raining but it takes hours for tall grass and brush along the trail to dry out.

I usually don't bother with soft shells unless I'm taking a non-breathable rain jacket. The hard shell works just fine to keep the wind out. I remember one cold, windy day when I couldn't figure out why I was so cold inside my Red Ledge jacket. Finally I realized that I had left the pit zips open--just a little too much ventilation!