But seriously, saying he is weaker than Illidan and comparing him to random bosses is sacrilege imho haha. Lei Shen is really strong, maybe stronger than any other mortal warrior (as in Varian, Garrosh, etc).
"There are two novels that can change a bookish fourteen-year old's life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs." -Paul Krugman