That's still the basic idea. The roster generally remains full of either your orcs or enemy orcs. They are... fodder. A means to an end. It's not really about killing them so much as it is about using them to conquer the map you're in, or pitting them against other orcs.
I'm a big fan of dominating a captain and then at random picking some other captain and telling my orc to kill the other one, and then just seeing how it'll play out.
I guess for me the draw is probably similar to whatever drew the ancient Romans to gladiator battles. I love being able to just sit back and watch a contest to the death when I know there's nobody actually being hurt.