Doug makes some great points. I think by this point in the discussion folks probably realize that getting wet is invevitable - the comfort and enjoyment will depend on how you manage it. I think folks also realize that there's going to be a little weight penalty in the wet season. As noted earlier, even famous Ray added about 4 pounds to his 8 pound load when he did the PCT through Washington. Gear has changed a bit since then and I think that penalty could be a lot less now, but it's still there if you plan on the West side of the range in the wet months and a "normal" forecast.
Doug's plug of a big tarp can't be overstated. Especially in pair/group hiking. There's nothing worse than spending every minute in a shelter - especially disheartening in a small shelter. When we were running trips with clients in ONP, we always carried a huge 12x12 tarp. It was light for the time, and it saved more than one trip. Huge tarp and a fire can go a loooong way to making a trip enjoyable. Hell, the rain is even a welcome addition in that setup - I love the sound of it beating on a tarp or tent.
I've since kind of combined the big tarp and shelter into one and use a Hex 3 as my primary shelter. 1lb. 12oz. isn't that unreasonable, and I can set it up just about anywhere, house a couple people, stay dry, sit up comfortably, and not feel like I'm trapped in a 7x4 square for 12+ hours in a stretch. If I was out with 3 or more people, though, I'd still be reaching for a big tarp and cover the entire camp social area.
Now, to find an ultralight stool so I can stay off the soaked ground/logs.....
Lastly, it's not like this all year. We focus on it because we're in it now and it greatly affects 9 months of our hiking, but summer here can be bone dry for weeks and weeks on end. You can also escape the wet stuff with just over an hour in the car. I just spent 3 days weekend before last near Potholes and Dry Falls and after a little wetness on the first day, spent it all in sunshine and sagebrush. There are even lots of microclimates on the westside - the NE Olympics typically get under 20 inches of rain a year - 10X less than the upper Hoh Valley.
I've hiked in Zion, the Wasatch, the Uintas, Death Valley, California Coast, Northern Minnesota, Massachussetts, Connecticut, Colorado, Arizona, and a few I'm forgetting. I could live anywhere I want, but I still live and dream about Washington. So we might dwell on the rain and wet (keeps folks away :) but there's no better place in the country in my opinion. Certainly it's a candidate for the most diverse hiking in the country: all in the smallest state in the West.