This. Think in the movie 300 terms.
Peon - Generic 1 hp. (Random persian guys)
Tougher Minion - DR 5+1/2 level. (Immortals)
"Elite" Minion - DR 10+1/2 level. (The freakshow thereafter)
Regardless of damage dealt, the first attack to break DR kills them, otherwise, they are bloodied, and die...