I know exactly how you feel, and I have the exact solution for you.

Let me preface the next sentence by saying, this is nothing against you, because I've been there, I'm only trying to help you. With that said, here is how to get beyond it.

Simply put, it's an attitude problem.

To elaborate:

When you join a game, wait for your team to pick what they want to pick, then pick to the best of your knowledge what will help you win the game the most.

Step by step it will go something like this: (as an example)

• Join in the game
• 2 people instalock DPS before everyone picks (sometimes this can trigger yourself or your teammates, don't let it trigger you, keep waiting for the next picks)
• Another player on your team locks Moira, but he/she is a Moira 1-trick
• The 4th pick is a 3rd DPS, leaving you with 1 healer, 3 DPS [in your head, this is all good so far]
• Now it's only you and 1 other person left to pick heroes [at this stage you should check out the profiles of the other players to see what they're likely to pick]
• You look at the other players profile who hasn't picked yet and see he mostly plays Tracer and Zen. So you pick a tank (doesn't matter what tank yet)
• As you predicted, this player picks Zen as your team already had 3 DPS, and his 2nd most played in Zen
• At this stage, you're left with 3 DPS, 2 Healer, 1 Tank.
• You're now at a point where you can make corrections to your own pick, some ideas might be: A) Pick Rein because your DPS is immobile B) Pick Winston because your DPSers are very mobile or needs space created to frag/peeling (i.e. widow)

In this last phase of picking it's important to not say the wrong things or to not demand anything of your teammates. Saying "Moira, can you please play mercy" is too demanding, and most of the time won't achieve anything. HOWEVER! Knowing your Moira mostly plays mercy, and suggesting to the team (politely) that your current team comp would benefit greatly from a mercy (even though every team comp would. LOL) may just get him to decide for himself that he wants to play mercy, which would probably be a huge buff to your team, and meanwhile no resentment or bad-blood was needed. On the other hand, they might not swap either, and you should be totally prepared and ok with that, DO NOT ask a 2nd time or say anything else here. Nothing at all.

After all this. It's just going to come down to you, not your teammates, YOU. Yes you might lose because you ran a dive comp all game with one of your tanks playing rein and refusing to swap. Or you had a DC or thrower(s), etc. But you can't win them all.