Two ideas that basically try to solve the same problem: A defense-attacking troop or hero that is between 2 defenses, one of them is under construction, yet that's the one it attacks next.
1) A "smart troop", one that can detect where the most damage it's taking in is coming from and attacks that first.
2) Any troop whose special ability is you can direct it to its next target.
Very valuable ability, so I would expect it to be very expensive to upgrade/train.

