His kit is just overloaded for an assasin.Yes,assasins should be able
to get in quicky in fights,burst their targets and get out.But the problem
with Ekko is that he can do much more than that.
He can shield himself,he can slow and stun multiple targets with his AoE
spell(W) ,his nuking abliity (Q) can also slow multiple targets and on top
with all that crowd control he can stick to with his passive so u can never
Assasins should quickly kill champs and safely get out,i have no problem with
that,but assasins also should not have so much crowd control and utility overall.
He is just basically Talon and Zed merged with Viktor into the one champ.
Also his ultimate should give him less healing.since it is AoE nuke spell and with
1.3 ap ratio and his main escape tool.
So imo,remove some slows from his kit or his ability to shield himself and then he
will be balanced assasin..