But if a unit or hero deals damage in the form of -1/-1 tokens, I guess the first damage world be absorbed by armor (if the target had armor 1) and the rest of the damage would be dealt as -1/-1 runes.
Also, I'd assume that buildings damaged with -1/-1 can just as well be tracked with regular damage tokens. Or should be? Can plague lab really aggravate the condition of the opponent's base?
I don't think there's a way for buildings to get -1/-1 runes.