You've got my sympathy! I know how you feel. I'm in the coast range in Oregon, and every ride has 100-125 ft of climbing per mile. My easy after-work 12 mile loop has about 1,200 ft of climbing in total, in three steep intervals. That's my easiest off-road ride.

As a mostly fair-weather weekend warrior for the last couple of years, I wasn't seeing much progress in my climbing fitness. So this year I decided I wanted to gain an impossible amount of bike fitness, and I set a goal to race in a local 50 mile (7,500 ft of climbing) race.

I have no problem gaining muscle strength just by getting out and climbing. A lot. But my limiting factor was always my aerobic fitness.

I've been completely amazed to find how much aerobic fitness I was able to gain by going on a lot of very long (2 - 4 hour) road rides that felt very easy (zone 1 / 2 HR) to me!

I still suck wind all the way up to the top of the mountain, and on most of the group rides I go on I'm still the slowest climber in the group. But I can look at my data from less than a year ago and see a significant improvement.

You'll get there too. It just takes time. I'd also recommend trying to find a riding partner who's maybe more your speed. I find it pretty defeating to always be going out with the really fast guys.