Who should I give Distant Counter to?

I'd do Sigurd.

i would suggest Myrrh, she is an amazing unit that benefits from DC over any other a slot, sigurd has other options (granted, so does Myrrh but DC is the best on her) also DC sigurd can be replaced for someone like Xander now that he is back, you cant really "replace" Myrrh with someone like fae because the 2 have arguably different roles
BUT if you need a res tank, i would go with sigurd.
besides, we might get another hector from the hero rise event meaning you can put DC on both

Myrrh definitely cause Myrrh is really bulky compared to the sigurd that you have. If you have a nuetra IV Sigurd, I would say you should give it to Sigurd but since you don't give it to myrrh.

Obviously it boils down to which you expect to use more, but going solely by units and their IVs, I'd say Sigurd. If optimal I'd say Myrrh in a heartbeat, but with those IVs... yeesh. She's still usable, but I wouldn't try and make her a DC candidate. Meanwhile, Sigurd can do some work as an archer/GMage check with that extra Res and DD3 seal. I'd go for him.

Using Distant Counter on Sigurd will prevent Crusader's Ward from ever working, (enemy attacks -> sigurd counters -> enemy attacks again, but not consecutively), so I wouldn't really recommend him. Myrrh would probably make much better use out of it.

I suggest Myrrh for the sole reason that a ton of people report that it fucks up Crusader's Ward (haven't tested myself, don't have the balls to waste a DC on a "test").

Also, Myrrh only really shines with DC, so you can't go wrong with her.