As player we use our soldiers as a unit, working together to win.
It would be way more interesting when the enemies would exhibit similar behavior (within their “character”).
One example is in the “HALO” game, where grunts were much more confident when joined by an elite. If other grunts or the elite were killed, the grunts also got into cover or ran away. This mechanism could also take into account their line-of-sight (or at least knowing where the other crabtree are).
Isolated crabtree enemies would be ok, but when they start working together things would change quickly on the battefield. Especially if they were to be able to attack an isolated soldier. And when the crabtree queen arrives they would be more inclined to come out of theire hiding/safe positions and full out attack (as the queen would order).
An additional level would be taking into account the experience (or reputation) of the human team. An experienced/hardened team would inspire more fear and careful attacks while a newbie team would inspire more (plain) single-enemy attacks.
