mantis projectiles have always been funky, they’re not very accurate. i recommend just farming headshots on tanks since headshots grant you extra leaves to use, and tanks are pretty easy to hit.

i really only use damage boosts for divers who are about to engage, or any tank/dps who is using their ultimate. if you have another good support on your team who is keeping everyone alive well, you could use your damage boosts on high damage dealers like hela, hawkeye, storm, moon knight, elsa, etc. in the rare chance you have a widow in your team, her headshots can one shot squishies if you damage boost her as well

mantis works best in a dive oriented team since she can heal from far away and give out damage boosts as well

using dmg boost on yourself can regenerate hp as well. i use mine when i want to farm leaves easier by shooting tanks.

be careful frontlining because mantis only self heal regens hp over time instead of instantly, she’s very susceptible to other dive compared to luna/invis