Hate to admit what I have been stung, bit or poisoned by, but I'd say I speak from a place of experience. The larger the fish the less it hurts. been hit by a foxfire that was the cutest little 2" thing that brought me to my knees literally. The intense pain was like a flame on my hand for 30 to 45 minutes followed by some strange physical response to the pain. And yes I had vinegar and hot water on it in seconds. I have also been hit by an adult that was less than a bee sting. In talking with some others the prevailing theory is that older fish have more control on the amount of venom they release and younger fish have less. A baby fish is also more scared and hits you with everything and an adult gives you a warning shot. This theory is based off of experience mine and those spoken to. As well as taking into account the cost of producing venom to the animal. My experience takes into account fish and spiders bites or stings, the others are 8 fish geeks, 12 snake nuts, two spider-men and a fan of all things venomous(Can't believe he's still alive actually)
So how big was your foxface that didn't hurt a ton? Does it fit our hypothesis