From what I can tell +damage effects from armor-slot items aren't working. You can see I have +poison damage equipped but only the +cold damage from my GZ is being done.

Er, let me check on this. The way it works is it will show the dominant element's color. So if it's 20 cold and 5 poison, it will do the resist calculations separately and then add the numbers. Since cold is higher it will just show a blue pop-up to save some stress on the browser. Plus it would kind of be a GUI nightmare to see so many pop-ups if you had all 5 element types. But I will check to be sure armor is getting added.