Possibly but it also comes down to first turn and also other elements in the game
Those who judge without reason are no better then the things they judge.
Khorne doesn't get many options for "ranged to combat ranged" though really... What else would you suggest he add to his Khorne build to be better suited for ranged? He has the stoker to move em faster already. That should help minimize the damage and close the gap... hmmm
But yeah you can pretty much bank on your dudes taking a wacking when a storm of arrows (etc) comes in. I would suggest at a minimum increase your unit to 25-30 Bloodletters so that you can keep the 20 minimum for your bonus when it comes time for the hand-to-hand, or if you end up on the receiving end of a charge!