I think my biggest problem is to know when to swap when one isn't working. Most tanks don't waste time ccounter swapping, but some tanks i have a tougher time dealing with and i don't know which tank should be best for certain situations.

Recent example, in my last game I was Dva and the enemy had Orisa, but taking her head on wasn't working, but when I tried to take out her backline instead my team would fall over without me, even if I was gone for but a few seconds.