Generally speaking I think it's good to not get too used to playing in a group because you will get too used to particular habits and tendencies that will not carry over to solo queue.
Solo Q won't be kind to you even at diamond, I'd argue that's even less kind.
Find a couple of good teammates to group up with.
Diamond is a strange anomaly where the quality of games is really low because player skill levels are all over the place. I can't quite put my finger on why this is but I digress.
If you're good enough and you play enough games you will eventually get through it. Many people - including myself and Antitrop, as indicated earlier in this thread - have solo queued their way through diamond.
Of course, a fair few players actually belong in diamond, which is tragic because it's an unpleasant place to be.
Don't shun me but I always have more fun in solo q than with a group of my friends. Mainly because we're a "mixed ability group" and they fucking frustrate me. At least in solo q people are generally a similar skill level to you and mostly competent. As a healer diamond healer main, playing with low plat dps can be cancerous. I duo q with 2 of them from time to time because they're near the same sr as me, but if I had kept playing comp with them and not going through a solo q grind, I never would have improved at the game to go from gold to nearly masters last season.
I have two close IRL friends that play this game. The closest one to me in SR is about 2500 SR lower than me. One of them likes to play Lucio. He beats after the fight is over a lot.
In short, I can sympathize.
