IMO:

Usually with same skilled players u wouldnt go as tracer as she is countered by bastion, genji is best counter but a lot of other heroes can deal with him 2. As for mei counter anyone with high dps, or fire rate can destroy a mei. As for difficulty for learning curve of being good with players, genji, mei, zen, zarya.



Assassin

Genji



Defence

Mei



Tank

Zarya



Support

Zen



My recommendation would be to play all heroes and work out their strength and weaknesses so you can counter them either with direct counter or hard counter. Also to be good player for your team if your not going in as a pre-made try to learn 2-3 heroes for each role.



For learning 2-3 heroes for each role you can be prepared for each game-type or scenario, because different heroes work in different scenarios and team compositions. In saying that map knowledge and usage is good as well and this will all help to getting better at the game.



This wont guarantee 100% win rate but it will help increase your current win rate, remember its not a tdm its objective based game currently. So those widows out there that dont contest the point when the team is on the way back and you about to lose just contest it as it may give enough time for your team to com back and win the fight.



GLHF ~See you out there