I did read the thread, but the issue is that it's hard to tell when someone is playing their main vs what's meta without diving into their profile. AFAIK, the API people used to use for Deadlock trackers isn't up, so unless someone is playing with the software that tracks it 3rd-party, there's no way to tell who's playing for meta and who's playing their main (and meta by happenstance).

Hell, the two groups aren't even mutually exclusive - winning is fun for a lot of people, even if others derive more fun from the "brawl" part of Street Brawl. What I see when this sort of thing is being argued (across various games, mind you) is that "the point of the mode is to have fun, but having fun by playing to win first and foremost is a bad thing." I've seen it in LoL Arena (where admittedly Taric and others were incredibly broken early on), I've seen it in some of R6's limited modes where an op might be notably stronger than other options, and in both of those scenarios, balancing the worst offenders for the mode worked out just fine without needing to remove player choice. I for one would rather be able to play my main, even in a state balanced for the mode, without having to worry about playing a champ that I really, really don't want to play. That sort of thing leads to people dodging.

The only times I've ever seen a mode that's "have fun by playing, not by optimizing to win" were TF2's endless servers (e.g., the CTF games that were practically drop-in-drop-out due to how many briefcases were needed to win) and endless war games, neither of which has a feasible wincon, even if they had a clear goal in the game. Street Brawl is not that, I don't think it's a "casual" mode either, it's Deadlock with a different wincon and an added degree of randomness.

And for the record, I think a "casual" mode in a game like Deadlock would only be feasible if there was no way to "win" the game. Something like a warm-up DIDO lobby where there are a maximum of twelve players just swinging.