I believe, along with many other players, Duo Q causes a problem for lots of people in the game as they take up 40% of the team. Don't get me wrong I also enjoy playing with a friend in ranked, however the _majority_ of premades are very toxic as this is two people that will rage at your mistake, plus they will never pick up on each others mistakes.
This isn't even the worst part, if you were to take the _majority_ of the premades 'roles' you'll likely be raged and flamed, plus chances are you'll be reported which is extremely unfair as premades are abusing the fact their premades and thinking of themselves as superior to others no matter what their pick is. I personally have experienced this to the point were both premades flamed me all game and fed pretty hard, plus the fact the 2nd premade player decided to troll as support taking cs :/ sadly their is nothing I can do about this and I'll admit I was toxic in this game, but wouldn't anyone be after be insulted too much, the worst part about this is that I got a 2 week ban from them after I flamed due to being provoked.
tl;dr Most premades abuse their 'power' and it's two people flaming you for each mistake you do. I either believe there should be a Solo Q option only without premades or premades removed all together from Ranked. Thanks for reading ^.^ (not bashing all premades just the majority)