My preferred method of handling this would be 100% chance to cause burning on initial encounter and 100% to reset the burn ticks on each pace through burn and each pace standing still in the fire. Never re-apply the initial damage when moving through or standing still though, just the DOT.
It doesn't make any sense that you would take additional damage from running out of a fire but you would by simply standing in it until it subsides.
If you have the debuff and already took the initial shock, you shouldn't take the initial damage again until the debuff is cleared. It's madness.
