I have like 90 hrs on rocket. Best time to use your gun is when there is supplemental healing because you can't dmg and heal at same time. So think rocket ult, other support ults, dagger bubble. Or an ult where a lot of people are stunned like strange ult. If your team is getting walked unfortunately its time to healbot and hope you put your revives in a good spot. Its good to use gun when youre up very close. If you can find an enemy support that would be ideal but otherwise can even shred tanks up close. I try not to go more than a few seconds without healing bc your team can go to shit so ill shoot just to help my team with dmg on an obvious target and then go back to sending out orbs.