MMR Penalty For Duoing Needs REVISION
Duoing creates a massive imbalance in match making and you won't always have a duo on your team. The average MMR penalty for duoing is reasonable ONLY in the average case for duos. However, duos with well-practiced strategies (perhaps funneling), good synergy etc. have an incomparable advantage to the MMR penalty. Thus, the MMR penalty should INCREASE if a duo players a lot of games together and wins (not just 2-5). Their advantage only grows as their strategies are refined. Essentially, duoing is fair if people are just playing for fun together but if they actually intend to climb and think about how to maximally exploit duoing, it becomes grossly unfair and the system should adjust for this once it's obvious this is happening.
Moreover, it's unfair for solo players because win rates, KDA or rank are not reflected in any way to show whether someone duod or did it solo. It treats all accomplishments as equal when they really aren't at all. There is no separation and there really should be. Duo games should be marked as such. It's just absurd to treat them the same as solo. This isn't getting into the unfair matches duos can create. I think duoing belong in flex queue because it distorts the ranked system. I've just seen a duo go unranked to D5 with 80% win rate without funneling. Their mains are ~D3 solo with just a tad above 50% win rate. This took them around 40 games and just highlights how completely broken duoing is when your motivation is to optimize climbing. They even said they couldn't get anywhere near that performance solo.