DC, Warding Breath, and Swift Sparrow.

Swift Sparrow is generally used for sweepers that have some bulk they want to preserve. I run it on my +Spd F!Morgan and it works pretty well. Other good candidates include Innes, Caeda, or basically anyone who's fast with good bulk.

DC's a tough one as there are many strong candidates. I'm not sure what you have, but some strong options include Myrrh, Ayra, Zephiel (or any armor really), etc. If you want to go non-traditional, there are some cheese builds with frailer units like Hana. Go with what you like as there are ways to make pretty much any DC unit work.

While it's true that Steady Breath is generally preferred to Warding Breath due to the melee restrictions, there are still potent candidates for it. My biggest recommendation would be Lightning Breath Fae as she likes tanking mages anyway. Aside from that, I guess Fjorm could work given her high res, but yeah the melee restriction makes Steady Breath a better option generally.

Hope I helped.

warding breath for grima robin if you plan on swapping out vengeful fighter or adult tiki can both make good use of it. dragons and DC units make the best use of these skills but for dragons, Fae prefers steady breath and nowi can go either way depending on boons or banes.

if you ever manage to grab a +res ryoma, it might be a good idea to give him warding breath

for DC, i'd advise against robin and anna because their optimal A slot choice is fury unless you change their weapon.

For swift sparrow, i find it hard to justify giving it to a melee unit because they'd either want the bulk from Fury (i.e. Anna, Azura, Eirika) or don't even need their defenses so they're better off ditching them with LnD (i.e. Cordelia, Raven, Athena) so it's better off on a mage like Mae, Delthea, or Lute who can serve as a ranged tank but doesn't appreciate the recoil