You cover a large territory with "Pacific NW and BC". Climate ranges from rainforest to desert! If one has camped many weeks in the summer in the PNW and had nothing but "stellar weather" you have not been in the PNW I grew up in! Rain and rain+wind are two different animals!

The stats show that in eastern BC, you will get rain 1 out of every 3 days you are out, during the "good" season. Coastal BC, maybe more (I plead ignorance on coastal BC). Cascades - pretty nice in a narrow window of summer in some years. Coastal mountains generally can get drizzles for days; Rocky Mtn BC get that PLUS thunderstorms (read: wind). Olympic Penninsula- drizzle forever!

Another issue is altitude - are you planning on below timber or above timber camping. I do not agree that mountaineering tents are overkill - they are exactly what is needed for mountaineering conditions! Some of us "backpack" in mountaineering environments. Wind is a big issue here.

Get a basic light tent for 3-season, non-mountainering conditions. You need to get this kind of experience anyway before you venture into more hostile envivonments. You should easily be able to find a suitable tent under about 4.5 pounds. If you want to do winter or higher altitudes, save your pennies (or put it on your Christmas wish list) and buy a specific tent for this. I agree with others that there is no one tent that does it all.

My biggest criticism of tents for rainy conditions is the entry. Most, particularly the side entry ones, let rain inside when you go in and out. The tunnel type tents with an extended porch coverage seem to work better for me.