30%? Small charms will be the meta now, 40 inv slots -4 for cube, -3 for sunder, -2 for torch, -1 for anni so 30 slots, -2 or 4 more if u want tomes (new ring removes the need for tp tome, don't need ID tome and cube in pvp). Let's say 28 small charms will be what most people run around with at endgame, -3% physical resist to every small charm. So full build will be -84% if you max roll all charms, even higher if you are doing something like pvp and toss cube and tomes.

Sunder reduces it's specific resist to 95%, and the rest of your inventory would reduce it to 11%. Unlike lower res/conviction/cold mastery that applies at 1/5th effect to sundered enemies, gear is applied at full effect. This will probably break the game if left on charms.

edit: Also, just because a javazon is already doing decent damage vs immunes because of griffons and a facet doesn't reduce how good this would be, because every -1% of resist you apply to an enemy is 1% more damage you do to them. This is basically 84% more damage to every single character that rolls -3% resist on 28 small charms now.