You should know that Moira need to aim to deal damage instead of symmetra who just need to get you in focus for a sec then her beam will follow even if you are not in her reticle or Junkrat who has AOE damages.
As someone who has played Moira almost exclusively since she came out, I can say that anyone who thinks she is OP does not understand proper positioning. A halfway decent D.Va or Soldier can shut down any Moira and make them nearly useless.
Her right click DPS is not that much, and her orb is only good in small rooms. If you have decent aim and you choose the right places to fight, she shouldn't be that hard to kill.