Shattered Kingdoms

Group A consist of a mercenary and a priest (behind the merc), group B consist of a mercenary, a barbarian and a sorc, the sorc is behind the barbarian. Group A's priest harms group B's mercenary and both mercenaries begin to whack at each other.

Then, group B's sorceror casts a spell at group A's mercenary and because the sorceror isn't technically in battle, group A's mercenary aggros the sorc, but because he can't reach the sorc, he begins whacking the barb.

I'm not sure how this can be fixed, but perhaps by letting the auto-retaliate flag be nullified when the sorc's group is fighting. The seemingly random target change is very annoying and can take your entire tactic in a group battle completely apart.

Why bug? The merc is trying to get rid of any obstacles (barb) in order to reach the sorc. It would be a bug if the merc was holding a reaching weapon and was starting with the barb instead of the sorc (who in this case is in second row). Why random?

Because he is already fighting the mercenary... If used effectively, this could be the same as if the barb had just taunted the mercenary. This is not the purpose.

Yep, now I get it. It smells like it's the same problem with the bug about the fire elementals and changing targets that someone mentioned months ago. It should be the warlocks casting and not the elementals themselves.