Diamond 5 here right now, though I managed to get to 4000 master in Team League (solo queue) before it closed, and in low Master in Hero League and Storm league too.
First of all. You CAN solo queue (it is what I do the most, since 2015 or so). But you have to consider these points.
-First of all. DRAFT. You must ask yourself these questions. What map are you playing? Is it a soak oriented big map such as Temples? or a fight focused like Volskaya? What heroes are strong there? Make sure your team will have enough soak, and a hero to push hard when enemy is unaware (Sylvanas, Azmodan, Probius, Jaina… but only if that hero fits your team comp AND enemy comp).
-Brawl at mid lane at start: don’t do it if enemy comp is strong at early (garrosh, tracer, etc…), you have strong wave clear / siege at start (sylvanas, azmodan, probius, hammer) or enemy have lots of quest to stack (thrall, zuljin…). There is no reason to fight at start if you won’t get much value from it and enemy does. It does work the other way around too. If your team does have those synergies, you can force fight, but be aware of siege heroes such as sylvanas, and leave mid fast if they start soaking other lanes.
-Best way to rank higher, at least for me, is a hero who can double soak AND destroy at teamfights alike. Leoric, xul (i dont play him), blaze, and, in my particular case, Jaina (yes, she is great double soaker, and can gank most enemies alone when lv10, even someone like Arthas).
-Mercenaries. Try to do them on good timing. There must be good guides for that in internet. Only note I will make here: Mercenaries in dispute: please, dont overcommit. No need to lose a teamfight for a mercenary that won’t do much if you get it at the cost of losing half your team, and lose objetctive for that. Or even lose the obj. Only try that if your team is next to you, and you have strong zoning skills (Deathwing, Mages, a tanky Johanna to hold point…).
-MOST IMPORTANT THING ABOVE ALL: Communication and attitude. From draft to end (even when losing), speak with your team. Try to follow main tank pings, and if you think he does it wrong, say it polite, bring alternatives to table. You must play Hots in proactive mode. This is a team-based game with share exp. Act like it (if you don’t) or improve it (everyone can improve there, at least me). And please, dont spamm “gg” at first lose fight. I recently saw that in half the games at diamond, and those people only show 50 IQ or being 12 years old.
-Try your best, always. Even when your team is losing, you can turn tides to your side. If moral is low on your team, some words on how to improve should help. Very related to point above. Don’t flame or accuse people with reports, it won’t help. Even when someone trolled at draft and you don’t have either heal or tank. I won so many ranked games withouth those two to know, if people play in good mood, there is always a winning chance. I know is hard, but there is no better way to win. Remember you are playing not only against real people, but also WITH real people.
Ask anything you want to know further, and don’t take my post as the holy bible. See you,… on the nexus.