[Agema]

There's a 1% chance of a mistform being cancelled by an attack, and it's automatically cancelled if 25+ points of damage after protec are caused. I think flaming arrows actually cause two attacks (the arrow, then the fire). So that gives them twice as much likelihood of getting a 1% cancelling, as well as the chances that 25 damage may be inflicted on one of the two occasions.

It's possible that the fire and the arrow may be counted together for the damage, in which case 10-12 damage (AP?) plus an AP fire attack has a fair chance of causing 25 damage to unit with average protec in the one attack.