Ekko is the best-designed champ in recent memory
While there are certainly arguments to be made about the balance of his bases and scaling, I can't help but give Riot props for an incredibly fun champion design. Ekko is more fun to play than any other champion in recent memory, and I don't even like Assassins all that much to begin with.
Riot said their intent with Ekko was to create a champion that made players feel "smart" when they pulled off plays. Well, mission accomplished! Timing all of your abilities to converge on your opponent is both difficult to plan and execute, and extremely satisfying to succeed at.
Compared to other AP Assassins like Katarina, Ekko is decidedly more intensive in the mechanics and strategy department. He's powerful, sometimes frustratingly so, but never once do I feel like my death to an enemy Ekko was the result of the champion being overpowered and easily abused. Katarina can blow up an entire team in seconds, and takes only a fraction of the "smarts" required to achieve the same result with Ekko.
I can see how he may need some toning down in the damage department, but all in all, I think Ekko is the best-designed champion in the last year or so. He's unique, he's strong, he's difficult to use well, and most importantly, he's incredibly fun to play. Well done, Riot!