Ekko's ult doesn't hit me like I thought from the video
I think it should be different. The idea of going back in time and regaining health lost, as well as dealing damage... well, that's not what the video showed, and honestly I don't like it myself.
So, I have an idea for it.
Basically, you would get the ult, and then every X seconds you would generate one stack. Max X stacks(I'm thinking three).You could activate the ult, and then for the next sixty seconds you could jump back to that area, no matter where you are. It would be great for getting back to lane, Baron/Drag stealing with your dash, and it would definitely be a problem for LeBlanc... teehee. Now, the ult would be crazy annoying. So, you could set a position to go back to, but for the whole minute you can't reset it. Once the minute is up, you can. And, once you use a stack, you have an X second cooldown(thinking about 5-20 seconds).
I think this would fit him as good as you can get from the video, minus the idea of putting your enemy back in time... that would just be OP. But yeah, in the video, going back in time never dealt damage(obviously) or affected anyone besides going back in time(again, obviously), and the pain of the injuries Ekko took never went away, unlike the game version.
Anyway, this is just my opinion. Tell me what you think, opinion, yadayada.