Originally Posted by elcruxio

There certainly are waterproofiing fabrics which are also quite breathable. But it does depend much on exertion levels. When wearing rain gear one probably needs to slow down a bit to control excertion levels so as to not overheat. But the same is true with every shell layer. Then again, one usually only uses a shell to combat cold so the overheating problem does not occur as badly. However fighting rain is a bit different.

Getting wet with wool can work, but honestly, I'd rather keep myself, my shoes, feet, underclothes, chamois and all that dry, especially if expeting a longer period of rains /dampness (of course depending also on temperatures). Getting into a tent with wet shell and dryish undergarments is so much better than getting into a tent when sodden wet, even if the wet stuff is quick drying / wool. Getting stuff dry when they are really wet can be a true challenge. In the military we had wood stove heated tents and clotheslines inside and still struggled to get all our (wool) gear dry during the night. Other fabrics than wool were just doomed to be wet for the whole trip to the woods.
Being wet for a week is not fun. Longer than that and it escalates pretty quickly.