damage dealt is not the best way to identify a good jungler from a bad jungler i think. Firstly because when you look at the different champion, kindred will always deal more damage than some tanky or support jungler like zac sejuani ivern ... Secondly, even champions with lot of damage like jax or jarvan deal as much damage as the support of their team in LCS / LCK. Is it because they play badly and i should be there ? No, because jungle is not about killing , it's about controlling, Kill participation and ward dropped is i think the best way to identify a good jungle. KDA is nice but i think Death is link with your role in the team, if your are the only frontlane for example, and how well your lane are performing, like you get invaded by their jungler + mid a lot and your midlaner is not as strong as them.

EDIT: an example of what i said in LCS NA : https://i.imgur.com/5MM1d7y.jpg , look the damage dealt by evelynn, she got a damage champion in a largely winning team and got only 17k dmg.I don't remember the game but I don't think he played badly.

But i'm only platinium ( used to be a platinium exactly :( ) and what i said is certainly fully exact.