Who should be the 4th in Armour Emblem?

Personally, I think armor emblem is bad unless u have someone with armor march. It is very easy to deal with them and they can get easily swamped by units. I personally would just wait until u have someone with armor march. Dancers really don’t help much. Tana could be useful with her c skill, but if you really need armor emblem for some reason, both units are fine.

why not go with 2 BK who are build differently, buffing each other up.
its something i considered as well, could be fun.
armor march would be good, as its a slow moving team. but the bulk would be insane
give them swap/pivot as well to get them into position faster

I love armor emvlem, it's my fav. I use hector, effie, zeph, and amelia. I really dont use armor March though I probably should. It's easy for me though since all my heroes can distant counter.

I'm also feather grading Sheena to 5-10 cause I like her.

The only emblem I don't play is cavalry although I have the tools for it.

Armor my fav and then flier and then mage.

I use Tana and it works out pretty good. u could also give her renewal and ardent sacrifice to be a healer.

I would suggest Zephiel and turn him into a pseudo healer. Give him This:
Echesachs
Repricorial aid
Bonfire
Distant Counter
Renewal 3
(Armour Skill)

I don't think a dancer is really worth it in most situations. I'd go with Tana if she's a option - my favorite hybrid team is two armors/two fliers and that's before guidance (just reposition on a flier helps armor tremendously).

But I have to suggest Healer Gwendolyn/Sheena as well.