To be clear, I'm talking about dynamic queue being in place but premades of 4 being banned. I don't think people would complain nearly as much about 2 soloq players getting matched with a premade of 3. It's the premade of 4 that drives 90% of the annoyance IMO. That event where you're the "odd man out". Any smaller and there are at least 2 groups ... or groups and solo players so the teamwork bar is more balanced. Plus it's infinitely easy to "fit" 3s into a game than 4s. 4s complicate things too much mathematically. Drop them and queue times will improve significantly regardless of rank.
As for role selection, so what? 27 MILLION players a day. These aren't trivial numbers. Yes you divide that three ways (roles, rank, groups) but when your mix-n-match is in the millions you should still end up with buckets in the hundreds of thousands for vast majority of peopel looking for a match. Leave roles in there ... it's doing very little.
Now granted at challenger tier you have a hard limit of 200 people. There I see a real problem with the system breaking down due to division vs sample size ... and that was a big part of the roundtable talk. But the disdain of DQ goes much farther down than just the top tier players. Everyone is annoyed by it. Again: i think the biggest annoyance is 4s, drop those and queues across the board will decrease as well as making the "odd man out" scenario no longer a problem.