The damage output I find hits higher numbers with attack speed compared to just focusing on CDR, Penetration and raw attack damage. You'll find Batman boost to attack damage in his ult or in a platform adds a good percentage to make up the raw damage part + the number of strikes & % you'll hit with critical damage allows for alot of 1 sided fights.  I find CDR is wasted due to it only helps 3 of batmans 4 skills due to martial arts has a required wait time for a charge (unless you kill or get an assist) to see a signifigant cdr you'll need to remove lobo chain + Zeiss Goggles to see anything signifigant (in my opinion) Items like Claymore or Hunters time Pack can or will replace Lobo Chain if the game is dragged out but after more than a handful of games this batman build does better than someone who builds raw damage,penetration,cdr due to I'm reaching around 1.55 - 1.80 attack speed compared to an a defending batman going armor and raw damage .90 - 1.20 It also helps if you replace dooms stolen power with superman adding in the extra 12+ damage and stun or slow depending on enviromental objects you throw.

I am not a fan of attack speed on assassins, I preffer raw attack damage, penetration and CDR. Can you explain me a little bit why you prioritize the attack speed?