Thanks for the suggestions. A couple of comments:

• I use straight bars, not drops.
• The bike is an 8speed.
• The derrailleur I currently use *is* a long cage derrailleur, not as some mentioned a short cage.
• I don't have a free choice of chainsets because I need 165mm cranks.
• My load on the climb was around 10-15kg (2 panniers, 20 l backpack). There are one or two items that I could have left at home, but that wouldn't have made a big difference. For my big tour, I'm going to need to take more - so reducing weight is not an option.
• I wasn't aware that I'm unfit. I have been cycling 60-80km per day through varied terrain with an average speed of 12-14 km/h, although rarely any steep climbs. On the tour in question, I climbed around 700m over ~15km with almost no level sections.

After reading all posts, I think I'm going to switch to a 24-36-46 chainset, in addition to the 11-34 cassette.

If 24-34 gear should prove still to high for my taste, I will give the Mountain Tamer a chance. Interesting concept. Just not sure how this is supposed to work with a non-friction shifter, though...