If you want to nerf Ekko jungle, just remove his double passive damage against monsters.

EKko jungle is clearly the issue. If we want to keep Ekko strong mid but not completely ridiculous jungle, the obvious solution seems to be to remove his double passive damage against monsters. This would tone down his clear speed and the amount of time he can spend in the jungle without having to go back and heal up. I think it would be ok to keep the double damage against epic monsters, though.

If he needs further nerfs, I'd recommend his damage, honestly. Ekko was supposed to be a utility assassin, Riot, a champion that traded damage for CC. He's not supposed to 100-0 with his E Q passive combo. Tone down his basic combo damage, but keep this ult damage in place. He should still be able to decimate you if he's smart enough to get it on you/you're dumb enough to step on it. If you go the damage route, don't touch his W. I think reverting the E damage buff would be a good starting place.