Scabies is useless and more trouble than she's worth - she recently transformed me into a pork golem and I had to summon a mistress from Nefas to keep me safe (granted, the floor was almost empty, but you never know when new monsters spawn). Does the monsters' leprosy spread to you if they hit you enough? Because if it does, then it makes her truly terribad. Also, the only way to use leprosy would be to cast it when you enter a level and then wait a long time, which is just not how I tend to play IVAN (particularly because you are eternally racing the clock for your AGI stat if you have natural limbs and aren't unburdened, or even if so).