Here's how I made the rancor meet his maker. Using stealth I snuck up behind him and laid a mine, went a few feet back toward the entrance and laid another mine..etc, etc. until I had about four or five mines. Once my deadly path had been laid down, I taunted him with a single rifle blast. This seemed to get his attention and he came running after me....BLAM, BLAM, BLAM, BLAM....THUD...he dead!!!
Famous last words "...Wanna see something cool!"