I played one last time in the beta myself with friends just to see if I still felt the same about the game. I just wish there was a 12v12 mode at least on PC. The fact the title is on consoles at 6v6 makes me skeptical this would ever be explored.
The TF2 pub server experience at 24/32 total players is just much much better to the drop in and fight style of gameplay compared to Overwatch's equivalent 6v6 solo pub experience. TF2 competitive play capped things at 8v8 or 6v6 I think, and I have no problems with the notion that competitive Overwatch is best played at the size of 6v6 with all the intentional class swapping required to execute whatever strategies a team might want to use to manufacture synergistic advantage.
Expressing to my friends that the game demands you counter pick, especially if no one on your team will, was frustrating at best. We had the most pub fun in brawl mode, but the unfortuante thing about brawl mode is that you see far fewer ultimates. Every time we'd queue into a normal game, I constantly had to counterpick Bastions (among others) that my teams could only die to because there is absolutely no way certain heroes can kill him given equal skill level of the players.
TLDR; If pubbing was 12v12 with bigger maps, there would be less pressure on any 1 player to character swap to the role their team needs. It also increases the likelyhood that at least 1 or 2 counters of any given character will probably be active on the map. Players should not be so heavily punished in a pub setting for not running an ideal comp, especially if the opponents actually do. With only 6 players on a team there are so many combinations of horrible compositions that it made pubs way less fun than I think they otherwise could be.