A thought or two, based on personal experience.

Skinnier tires = more pinch flats. The heavier you and your gear are, the more true this is. And fixing flats is never a high point of the day.

Compared to road bikes, purpose-built touring bikes will likely have thicker frame tubes around the bottom bracket, i.e. down tube and seat stays. They will also have longer seat stays and, partly as a result of the stays and partly of a longer front-cent, a longer wheelbase. All of this combines to make a more stable bike under load. And when you are under load, carrying anywhere from 15 to 40 pounds or gear, you want a bike that will hold a straight line even when you are slogging up another $^#*%@! hill 75 miles into the day when you are making a blistering 4 mph. At that point, it is stability uber alles, as the last thing you want to be doing is wrestling the bike to maintain a straight line. Stability, not a couple pounds off the frame or crit-bike responsiveness, is what will conserve energay and leave you felling good at the end of the day.

Also, what's the hurry? One of the joys of touring is the singleness of purpose and absence of demands. All you have to do is get there: you don't have to get there fast or get their first - and if you are touring with camping gear, odds are you can be incredibly flexible about what "getting there" means on any given day. Embrace that. Don't let your tour become an exercise in trading one rat-race for another.