Multiple armor marchers for armor emblem?

What I do is to give one of my units armor march (in my case Zelgius)

It could work, but it's better to go for more goads or wards

Armors are supposed to clump together after all.

Yeah you only need one. For me I use my Amelia to give Armor march to my allies. It just takes good placement of them to make sure Amelia is always in the middle or at least next to Jakob.

It all depends on you and your team. I run two Armor March units along with a Fortify and a Hone buffer and it works perfectly for me and my setup.