Oops!
In my next to last post,
Star Wars Battlefront II, I was wrong about two things.
Number one: the Rancor doesn't just stand there and roar. If you get too close to him, he grabs you and eats you! I was right about not being able to kill him though.
Number two: although it is extremely difficult, it is not impossible to win the Assault Mode in Mos Eisley while playing the villains. I won it once (I had the AI mode set to Elite, though; maybe that makes a difference).