Nose For Trouble

Procs once from the first hit of each individual enemy that hits you. Getting hit by 10 enemies means you could prevent damage up to 50% of your max health.

Does not reset after leaving combat, nor will it reset after dropping combat, getting in combat with something else, killing it and coming back to the previous mob. There might be a timer for it to reset, but if there is it's more than 5 minutes.

It only procs on attacks that hit you. If you dodge immediately you will still absorb the next hit.

how often does this proc,
resets after getting out of combat
or every new enemy
can a priest bubble prevent proc

Provided you have a fast enough mount and your enemies dont hit particularly hard, this is actually useful for avoiding dismounts as a vulpera, as most enemies wont do more than 5% of your hp in one strike, and they usually only get one hit before you move out of range whilst mounted