The issue with a carbon frame for touring is the thing which makes it a great material. Ie. you can design it to very specific tasks so that you stiffen up one axis whilst leaving another less stiff (not that I think that makes a lick of difference in a diamond frame but that's another discussion).
But on that point you also have to design a carbon frame for the intended use case ir the stresses caused could cause failure, especially with a lightweight design. That is of course true with all materials but the design element of carbon kinda emphasizes the point.
For example i read somewhere that certain manufacturers forbid the use of trailers on their carbon bikes because the chainstays aren't designed to take the directional stress a trailer arm could cause. Makes sense since a single carbon fiber filament is only strong in one direction and if haven't strengthened certain directions in pursuit of weight and because the use case doesn't require it, then those directions are going to be surprisingly weak.
So essentially a carbon frame would be excellent for heavy loaded touring if designed for it. If not, then it's basically up to luck if the design allows for it. But cheaper carbon frames tend to use more material = heavier = probably more durable in general.