The blennies and gobies and dragonets very rarely get ich. Tangs and rabbits get it very often. Clowns frequently get it but most other damsel types don't get it as readily, and a clown that has an anemone is less likely to get it---in my experience, on the latter: I think it's because living in an anemone increases the slime coat.
The way I've had it explained is that the bottom-dwelling fish like blennies and gobies have a natural defense against this plague, which is also bottom-dwelling. But the open-water fish like tangs and angels and rabbits don't have a thick coat, have no defense against a sand-borne parasite, and will get it at the first opportunity in captivity.
Personally, I keep my tank to gobies, blennies, dragonets and a damsel, and don't have any worries about ich.