Quote:
Originally Posted by Grotug
I thought it was a little under 100, too, but I just realized why it can be above and that is the variability of the average max hitpoints of monsters. 2400hp is the average for AMHDs, but there is at least 10% of variability to it (maybe even more?), meaning 2740 is possible. I'm not sure the formula for hitpoint generation, but I always forget about that variability. Something to keep in mind! 2740 hitpoints means fire breathing of 101 is possible, but I got hit by something like 111 which would mean its hitpoints were at 3,000.

I looked up the hitpoint distribution and there is a standard deviation of approx. 1/8 of the average hp. The cap is at +4 std deviations so for an AMHD this means max. hp of ~3200, which results to 119 dmg with double resists. although only 1 in 65536 instances of the monster will have this many hp. Looks like the one that breathed on you was at least 2 std devs from the mean, so less than a 2.5% chance of getting breathed for that much dmg.
One minor thing to add is that these randomized hp do not apply to uniques, these will always have the max hp as given in monster.txt