3rd Hector was pulled, who do I put Distant Counter on

Finish Armor Emblem while you're at it ?‍♂️

Save it for an Effie to complete your armor emblem

I'd go with Gwendolyn as she can help bait units like Celica, Sanaki, and Y!Tiki, which Hector cannot most of the time. Not to mention, despite Sheena's really good Res, she would either die to or live with very low health against red mages and red dragons.

If you have her, you could also give it to Effie. However, you'd probably need to invest in giving her a Brave Lance+ first.

Either way, go with QR 2 (or 3) in their B slot. It works wonderfully with DC.

Give it to your Camus. Trust me.

On a more serious note, Try giving DC to someone that has ridiculous unused potential. Maybe Chrom? Never seen him used, although his high attack can be salvaged w/o an A slot

Also, you lucky Dastard (FE Veterans Triggered)

Don't wait for an Effie unless you're going to do serious work patching up her defenses.

Gwen is a better choice for DC, especially with Berkut's Lance, but I'd love to see Selena fully decked out. Tough choice.