Statikk is the real guy to talk about this, but here's what I've gleaned from talking him to about this:
Draven's laning phase is stupid OP, but his late game is pretty rough. Spinning Axe is really fun and awesome and we always want that to feel good. However, the extra damage he's getting from the bleed is fairly underappreciated and doesn't really scale all that great into the lategame. We looked at the numbers and said two things:
1. We don't want to touch Spinning Axe.
2. It's hard to find numbers on the bleed that look even remotely good for Draven players while simultaneously having a meaningful impact on his early laning.
So we want with a fun mini-game where Draven farms up stacks and then has to cash them in by executing someone. We want the overall changes to be a net nerf (he's OP), but not much. There is a lot of power lost by simply ripping the passive out. We want this passive to be meaningful and have impact for Draven.
For example numbers, Statikk got Adoration up to 100 in just 5 minutes of laning from last hitting and Spinning Axe catches, and he's not even an expert Draven. This number is going to get high.