Well for me i only use it when im playing against a soraka. but eveytime i would atk her she would just wait tell it was off, which is only like 1.5sec.
I dont really care if it gives me crit, ad, or even atk speed. I just want the passive. They really need it to be longer tho, cause why would i want to atk one person but yet have everyone elsse healing up(from soraka's ult) i mean if it was 3-4 sec long i would buy it alot more but it forces u to atk someone every 1.5 sec just for some heal reduction( and lose out on some cs or something. i get its ment for a 1v1 item if they have alot of healing. but what about mundo? his ults last like 10 sec. should i have to atk him about 4-6 just to get his healling down? and thats not including if he runs out of range(think if a melee was vs a mundo)... its a item that counter healing not have me go out of my way to use it.