I find that playing with a buddy nets you the best results in ranked play. I tend to pick roles that are central to any team, which allows me to dictate the flow of the game and at worst, I can just turn off team chat and focus on synergizing with my partner.
I tend to go Ana and my friend goes Reinhardt, and as we are typically the primary heals and tank, the team tends to listen to us when we make shot calls. If the team refuses to cooperate, we synergize enough to where I can enable Reinhardt to become a bayblade of death into the enemy team. If we are on fleek, we can combo our sleep and charge moves to take out specific targets.
As for shot calls, I tend to avoid telling anyone who they should play as, and if I do, I color it as a recommendation. The most frequent one I do is the group up, and wait close to spawn until we have a full team, as most of the losses I have are due to our team trickling one by one to the enemy team.
That being said, I'm a cis-white guy, so that influences my experience a lot.