It seems quite interesting and may lead to some extremely difficult situations. Let's continue with your example. After killing the frog, then the player needs to roll a 17 in order to kill the wolf? If you follow this rule, it is just impossible to kill a lion unless you kill a frog and a wolf first.
Feel like you must scatter layer to layer in order to kill the core which is very cool and exactly what I want. This rule will require you to use the RC rule as much as you can in order to deal with the group of enemies or you may want to flee because the enemy is too powerful.
Sum up:
Group A
- Lion DS 9 (highest)
- Wolf DS 7
- Frog DS 2
The DS of this group will calculate like this:
Keep the highest DS, the lower will count as 1
Highest DS + 1 + 1
The DS of group A will be 9+1+1=11
- If roll 13 -> kill a frog (2), DS drop to 10
- If roll 17 -> kill a wolf (7), DS drop to 9(lion)
From now on, you can freely kill that lion.