Burn/Slow Damage Bonus Credit?

I use two firebombs on my Shooter (MK3) and usually get 3 stars at like 2-3k damage, even when my allies deal over 5k damage and have 2 stars.
It's easy star farming honestly. Dunno why it happens. According to ingame clues (Firebomb falls under Brock's perks) Firebomb is a defenders weapon, but I use it because of it's impressive radius, damage bonus for cannons, and actually good damage overall compared to other mortars which are more difficult to land.

Could be that the game encourages defenders and yellow ships (Slow Effect also grants bonus stars in my experience) to help out the team more, even with their damage.

 

Yes. The 20% extra damage he got from your example would be applied to your battle contribution for your star reward. This won't show in results but you will see that sometimes you will be above someone who did more damage than you.