What is the niche of every champion? [Riot focused]

As we all know now Riot is working on the Assassin Update coming this preseason.

They have said some small teaser-like things on the boards to give us an idea of what we can expect. One of the main things they have said us is what niche the type of Assassin delivers (e.g. is THE roaming assassin, is THE teamfight assassin) so you can think about what strenght you gonna deliver to your team.

But now comes the big question: What is the niche of EVERY champion? Yes, Riot did release a board about Classes & Subclasses a while ago but that doesn't say what niche a champion gives (especialy the hybrid-classed champions) like:

-What niche do these bring making them different from others? feels very similar to by being an tank that builds mostly defense to soak up damage and can engage/disrupt.

is known for his heavy hypercarry 1v5 lategame style, yet so does by murdering everyone on the screen with huge crits and AoE.

, infamous for his lategame splitpushing and hybrid kit, but why pick him when there is who can pretty much do the same thing the same way.

is scary because of his hard all-ins and disruptive power alonge with damage yet there is with the same concept.

As it seems some niches seem to overlap eachother, there are even more examples like or etc, so does Riot have a list that says:

" does 'X' so pick him when u need 'A', does 'Y' so pick her when you need 'B', does 'Z' so...etc"?

I would like to know if you guys know what champion does have what niche and type it below. And if a Rioter is reading this, please make a list so we have more clarity ^_^

-Thanks for reading and for your time.