Androxus' reversal isn't able to counter either, Guardian Spirit stun or Begone but his damage per second and having burst damage allows him to clean up kills on Io fairly Quickly. This is not to say that Io cannot body block with Luna.
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.
Moving Luna around is your best bet to deal with a Dredge. as for directly combatting him, your ult can save you from his ult if you have no way to leave it's AoE
Io's ultimate provides her invulnerability for a prolonged amount of time if you are trapped with a Terminus resurrecting using the ult to invuln through it, similar to Androxus' Reversal you can use your ult to wisk Term away before he can react.
Your sustain means nothing when Willo uses deadzone on you, your best bet would be to approach her when you have darkness to out damage her in the short run, in the long run of a fight Willo will almost always win