It's honestly really hard to say what does/doesn't work with how infrequent bans are coupled with the lack of responses from whoever is getting the reports for cheating.

I've personally been listing off every single player involved in what I assume to be joint operations when it comes to stuff like the Eureka bots, then offering a description of what makes it obvious they're botting (The way they tend to stand directly on top of the each other and move/cast in perfect unison being a big one).

It's impossible to tell if that's actually the "right" way to report them or not, though.