Disagree completely and therefore downvoting you.
1: There are tons of champions with skills that "redo" a misplay. Zed can just shadow away if he wants, Zac can just slingshot himself out, Udyr can just run like Sonic the Hedgehog if things don't look in his favor. Lee Sin can just Ward hop away, Fizz can just E and sit there and wait for his team. Maoki can just tank for days until his team comes. Literally lots of champions have escape mechanisms, or at the very least have implemented strengths tom survive bad situations.
Ekko's ult is telegraphed, and you can tell when an Ekko is going to ult more than likely, and already begin your quest on running towards the clone area just so you happen to be near when he ults.
2: It heals him, sure. It's not a good heal as people think. I got over 150k on Ekko, maybe 200k counting my other account, that heal is complete shit, people bring up the heal and I just laugh. By the way, hasn't the heal already been nerfed? It seems like I can take a ton of damage, then ult, and barely reach 40% HP. Out of all the times I've played him, I have only been able to reach like 90% HP only once maybe? Then again, I now and days build more tankier, so maybe that's why I don't see a big difference compared to a AP Ekko with less HP, but none the less, it's not that good of a heal. The heal is more or less along the lines of "hey I can stay in lane for another minute, clear and push out this wave and then recall back to base and buy stuff" opposed to a non heal fight where "maybe I should recall cause their jungler could gank any minute".
3: Are you really crying that a ULTIMATE does DAMAGE and lots of damage? AN ULTIMATE. You know? The R BUTTON? The thing you press when you want to feel like a god? Are you really complaining that it does damage and a good amount? Seriously? You're just nitpicking about everything at this point. If you get hit by an Ekko ult, you deserve every amount of damage you can take because quite frankly, I've hardly ever been hit by Ekko ults myself, its easy to play around, and 80% of the time, Ekko uses his ult as a defense mechanism and not as an offensive move. So for you to complain about this is quite laughable really. Also, Ekko's ult is hard to even land as an offensive move, only bronze players will be hit by it in some scenarios like if Ekko were to use Zhonya's hour glass for example and W and allow his clone to reach him, only low tier players would be hit by that and not smart enough to know whats going on. Anyone high tier, or lcs would never be hit by an Ekko ult like that. Now for the occasional I've been hit by an Ekko ult, that sometimes happens but it's rare, only time it most likely happens is in teamfights where no one is paying any attention which most people don't and always ignore the visual effects and such, but none the less, 99% of the champions got ultimates that do good damage, and over 70% of them can land their ults more often than not compared to how rare a Ekko can land his as an offensive tool.
I'll never understand why someone would complain about the damage from this ult compared to lets say Lux's where she 1 shots almost anyone? Or Vel Koz and his crazy burst ult, and so many others.