Pet Statistics There are a few ways to determine pet classes. With pet damage turned on a rogue's backstab is clearly discernable as single hits of double or triple damage among normal attacks. In the upper levels (60+) warrior pets will buff themselves with a short-duration damage shield.
As for disease spells (and poison as well) they work on counters, which are tracked on the target. For a hypothetical example, take a disease spell that adds 6 counters and a cure disease spell that removes four. You can cure the dot with two casts.