Koga can avoid Luna's stun so your best tool to handle him is to use Luna's large hitbox and healthpool to face tank his fire while taking chances to fire at him.

Farm darkness off of Luna will be a massive help.

Vora struggles to out dps Io's healing if she runs Life Link and/or restored faith, and is hiding around Luna which may allow Io or her team a time to kill you, to counter this attacking Io when Luna isn't around or killing Luna will work.

Your best bet is to stay back and try to farm darkness off of her shield. due to the fact that trying to hit below her shield will be near impossible due to your projectile size.