I dont remember if there is buff in latest patch on this Assassination card(I think it does i remember the total damage was divided by 8 now you changed to 4), I think the damage is too high. Lets see the formula below at level 1:
(250 hp deduction X target's base-cooldown)/4
For example if i have a CD 6 unit, it damage will be (250 X 6)/4 = 375 hp deduction! I just wonder how can any unit stand that kind of damage?? Hp deduction is basically ignore armor type and its at level one too

