Zed's ult passive from the assassin update sucks
There really isn't a more tactful way to put it. The bonus granted from it is so laughable that it isn't remotely worth influencing your playstyle. One might think it would be a nice reward for killing the ADC, but the problem with that is that ADCs don't buy a lot of raw AD, they buy attack speed and crit. When you kill an ADC that has a stattik shiv or Berserker Grieves, you don't get shit from that.