Gran Faust without the charge attack is a pretty solid weapon - partially because it curses on normal swings. It is possible to get armor that will protect you from Gran Faust's curse, but it requires both a MAX UV and some solid curse defense on the armor itself. I suspect that if you invest in armor in the divine side of the Valkyrie line (which has some pretty solid curse resist built in) with an anti-curse UV, you'll get your pain-free Fausting back. Is it worth it for you? Well, that depends on how much you care about the charge attack.

Nox, armor defenses and resists do not add up or cap in the same way that they do with weapon abilities. For example, using two items with max UV shadow is more useful than using one item with max UV shadow. I believe a max defensive UV is half as strong as a 5* item with a full bar of that same defense/resist.
Open your character screen and mouseover the icons on the bottom row. That will show your TOTAL current defenses and resists.

Actually, depending on the level of fire you can become fireproof. With my Volcanic Salamander Mask and Volcanic Demo Suit (Med. Fire Resist UV) I do not get set on fire by the fire trap in the Advance Training Hall. Some advanced tests have been done in this thread by the Wiki editors: http://forums.spiralknights.com/en/node/10522

Probably you need to have the curse resist box completely full.

You can be inmune to medium and low shock/curse/fire/poison and so, but not to strong statuses, so faust with the correct UVs makes you inmune fo faust's curse, but since grand faust causes you strong curse, you cannot be inmune, it just reduces the time of curse and how many swords and items gets cursed.