So, to my knowledge, Status resistance on armor and helmets reduces the chances of getting/effectiveness of whichever status they are resistant to right?
What does it do with shields? It's not passive is it? Does it reduce damage from attacks that would cause that effect while up?
I believe it protects you from the status effects while the shield is up. It's hard to notice on the hazard plates because it's masked by the direct damage the plates do to your shield. It's much easier to see the effect from status clouds left by monsters like greavers or ice cubes.
So, when dealing with the average status-inducing attacks, shield resists don't really do anything?
If you're inflicted with a certain status effect that your shield is resistant to WHILE GUARDING, the effects of that status will be reduced. If your shield has fire resistance, for example, but none of your armor has fire resistance, and you get inflicted with fire status while your shield is up, the shields resistance will have been factored in and the fire status will have reduced effectiveness on you.
Eh, not really so much on the less damage part but...
Let's say you have a Heater Shield and you see a freeze plate/status cloud. If you put your shield up, and walk through it, it will break less easily. Now if you use a different shield such as a Aegis, it will break easily as you walk through the cloud/plate with you shield up. This shield must be up.
You gain the shields resistance benefits only while guarding.