My big thing:
I don't recall the Klingons ever having pink blood in the series. It's always normal human red.
Also, aren't the Klingons supposed to be extremely strong and tough - not as warriors (though that too), but as a species? Isn't that the whole point of Worf getting beat up all the time - to prove that the enemy is even stronger than a Klingon? Yet they get taken out more easily than most of the human fighters, with the exception of any headbutts.