Just got a Ratfang Toxin and tried it out on Target Dummies.
The debuff applies all 5 stacks very quickly (effectively instantly), so it kinda makes me wonder what the point of the stacks are.
But more importantly, the stacks themselves don’t appear to have any sort of expiration. And they’ll keep you in combat for a very long time. If I attack a target dummy, and then walk all the way to the other side of Dornogal, I’m still in combat and can’t mount or stealth. I can vanish, but remain in combat. I don’t know how long this goes on for, but it’s at least several minutes, which is way too long.