I dont know if I would say these guys were more susceptible to ich than any other tang.
All tangs are ich magnets, I just think its more apparent on these guys because they are predominantly black.
I would have no qualms with keeping one aside from aggression, and the usual factors that should keep most people away from tangs...tank size (I think at this point I dont recommend anything less than a 125g for any tang. 75's and 90's possible for scopas or yellow), water quality (needs to be pristine...otherwise you will get ich anyways), and nutrition...see previous point.
I also think it is important that they be able to graze. This is 90% of their life in the wild, and tangs that are not given some sort of algae clip (nutritionally you should probably be able to get away just feeding NLS) fair poorly compared to those who are allowed to pick at something as they wish to naturally do in nature. (Naturally in nature. :D)