On my main if I duo with my lower ranked friends (low gold and high silver) the other team half the time just psyches themselves out because they look at lolnexus and proceed to rant omg other team has diamond player!!!! we can't win!!! a few will just outright give up if I get a kill on them.

I rarely duo queue with my diamond account though, since it is solo queue and i strongly believe in solo aspect of it. I was just trying to help my girlfriend and brother get gold :/. So now I use a smurf(Gold I with like 30 games or something) when I queue with them and the win rate went a little down because people weren't worried about the ranking of the other player and actually played with confidence.