This was driving me crazy on my last playthrough. If your characters take fire damage, they take 1-3 damage per turn. If you use dragon rounds though; the enemy only takes 1 damage per turn. It should have a range like XCOM 2. It's screwy that the rules are different for the player vs the faction enemies. Acid seemed to work the same way. But, by the time I got a single caustic round, I couldn't verify.

Another thing was during viper binds. When the enemy turn comes up while they have been bound by torque. They take no damage. Only on Torques turn do they take damage. While, if you are bound by a Python. You take damage on their turn as well as on your own turn.