A few points about the problem that is Duo Queue.
-You can master powerful duo strats. 1. Azmodan + Joehanna stacking. 2. ETC + Tyrande ganks. 3. Li Ming + Xul lockdown and burst. Illidan/Greymane + Abathur/Tassadar 4. Zeratul + Tracer
-The best duo boosters I've seen play "carry" and healer to keep carry alive. This is what Wiz and Hide did to rank up. Pick Greymane/Zeratul/Sonya and uther/reghar to keep him alive and profit. Just randomly go through the leaderboard's match history on hotslogs if you don't believe me.
-Duo Que can abuse smurf accounts by dodging bad games with the bad account (throwaway account) dodging.
-Nothing has changed in regards to "smurf boosting" The current system allows for players to play together as long as their accounts are within one league. At GM you can be within TWO leagues. Let's give an example. Let's say we have two Masters players who want to be GM but aren't good enough. So these makes a garbage smurf account that is tanked to stay diamond 5 (but with master level operator) this garbage MMR account queues with the Master level account struggling to get GM. The eventual matchup will give the enemy team a legit diamond 5 player to pair vs your master player. This disparity makes boosting the main account to GM as easy as about 30 games. Once GM you switch and return the favor. -There simply aren't enough good players in HOTS. There are only around 3 4k players queueing at any given moment. The system prioritizes just giving them a game over waiting. This leads to the 4k duo getting three 3.2k on their team and giving the other team five 3.5k players. There is a GIANT difference between a 3k player and a 4k player but not much difference between a 3.2k and a 3.5k player hence an unfair game.
-psychologically humans are suspicious of a singular individual but as soon as 2 individuals engage in a behavior they are 60% more likely to follow. (see link to study at bottom) Therefore, two people signaling to take boss, keep or gank are 60% more effective in coordinating their team.
-you are more effective in persuading your team to not pick a bad hero. You also have a less chance of a player picking a bad hero because you comprise 2/5 slots.
-Duo queue creates a sense of entitlement and exclusion. Most of the top players only play with each other. Try asking for a duo from most and they will tell you how much they charge for "coaching" or say "I don't know you"
This ends most of my points about the problems of duo queue. Hots is a game where one player cannot carry his team to victory. However, I strongly believe that two players do carry many of their games. This means that the solo queue experience will be much harder and much more frustrating leading to more people leaving the scene. Because I care about hots and because the vast majority of HOTS games are played by solo queue players I believe that Hero League should be for individual players rewarded for their individual efforts.