Yup, solo and group ranked is dominated by a small band of people who always get to top. Then they play so many games that it is hard to go through their history to check for the cheating. What they do is sync que, que dodge and much much more. it is easy for them to gain rating when they que as tanks, heals and so on. They also use bot accounts to leave que or match and many more dirty tricks.
The second issue is the mentioned account selling. That was quite popular, although I dont think its a thing now as the game is not so popular anymore so they cant be making money with this. However, I can say that bans are being made but I have yet to see rating resets for example.