Oh, and in other news, I just realized that you can stack Essences on gear to give pretty much everything you're wearing 25% resist-all. Or use a Ruby for 20% resist-all. This means two things:
1) For a properly built endgame character, even without Weather the Storm of full plate armour, you're going to be immune to every element. This is hideously overpowered and needs to be fixed.
2) Having every character functionally immune to everything but physical and Tenebrium damage makes Glass Cannon even more powerful than I first imagined. I imagine its power could be tuned down slightly by making it harder to stack resist-all, but the point is that it's an even bigger problem than stated in the OP.