I don't really think this is something that we NEED and it's not really important, but I do think it would be better if Barkskin and Stoneskin covered just the skin and not the armor. After all, these spells are described as changing the user's skin. I don't know how difficult it would be to change the coding or graphic or whatever.
I was kinda bored and made of picture of what it would look like. Took me about ten minutes using ms paint. Here's my elf wearing a mithral chain shirt with Barkskin:
Not a perfect crop but whatever. What do you think?