Game Master Theory

Yancey

Often, though - the min/max player will move to address the easier parts, which leads the group to be dominated by the larger threat.

I've experienced this issue a few times. More often, the tactic is to win by attrition by taking out the easiest opponents first so there are fewer distractions while fighting the main threat. This is often the best tactic.
My way of handling min/max is to present challenges that highlight non-combat traits. Testing knowledge skills or dealing with political situations, etc.. This rewards players who build more balanced characters.