Ekko is an engaging tank with built-in damage AND escape?

Literally, Ekko walks up front and jumps in with defensive items, brought the backline to almost dead and just zip back with a healthy amount of HP.

My jungler did some really good work as Hec, but when he tried to go in with our Renek to their backline, they managed to bring 1 down, but they did suffer consequences. Ekko did more damage to our backline considered his spells aren't exactly hard to hit, did a chunk to both ADC and mid and still walking around after ult, waiting to participate.

What's the deal on this champ?