Quartz
Hero
The issue here is that unlike a Disjunction, this is a continuing effect. A character who's had his armour disjoined still has armour; with Rusting Touch, not only does he lose hs armour entirely, but he can't put on new armour (which takes a long time - go look it up) because he'd rust that! A character who has his weapon disjoined still has a weapon and can swap it for another weapon; with Rusting touch, he loses the weapon entirely, and if he swaps it for another weapon, that may well have to save against his Rusting Touch too! Disjunction causes a pause; Rusting Touch causes ruin.