I've done credit-card tours with a 105 50/39/30 triple and 11-28 cassette. With no more than about 10lbs in a saddlebag, I found I could get up most things. It's much higher gearing than I would use for fully-loaded touring, but significantly lower than I normally run on my other road bike, when my lowest would be 36/27.

So it boils down to what sort of experience you want. Go ultralight and you can manage with taller gearing, but it is certainly a higher speed, less relaxed trip than one gets with a more traditional touring-specific setup.