Hi there.

IMO, there isn’t much point in playing Open Queue if you one trick Mercy. You should play Open Queue if you like flexing across roles, or like creating overtuned team comps with a large stack, or like want to play dps without waiting.

Role Queue has more stability in terms of team comp, and people generally take Role Queue more seriously. Still, OW is just a game, and you can whichever mode you like.

You already point out major mistakes you make. I would focus on one thing at a time. I would start with no suicidal rezzes. Keep playing QP until you don’t make suicidal rezzes. Once you avoid suicidal rezzes, start thinking about when it is ok to go for a risky rez.

Once you master avoiding suicidal rezzes, work on being the last two person to die in a teamfight. If Mercy dies early, then the teamfight is likely lost unless your team commits ults or get picks. I suggest keep playing QP until you are the last two people to die in 80% of team fights or higher. Prioritize your life over your teammates.

Lastly, there are always exceptions to general principles. But you need to know the rules before you break them. You could practice the two lessons above in comp, but I presume QP will be a less stressful environment to hone in fundamental Mercy skills.

In comp, you may think “I must rez now!” In QP, hopefully you can collect your senses and think “hmm… do I really need to rez now? Can the enemy team kill me while rezzing? Does the enemy team have abilities that can cancel my rez, like a CC? Is it even a good time to rez? Will the rezzed person quickly die after being rezzed?” You got 10 seconds to make a decision, so take your time, it’s just QP after all. As you get better, your decision making speed will decrease until you can know if a rez is good or bad on instinct.