This is not the first time Estel has tried to turn a bunch of undisciplined idiots into a coherent, drilled unit. It is, however, the first time she has tried this with a bunch of berserkers who think they understand war.
Fortunately, she is quite clever, moderately splendid, and has two moderately clever people she trusts absolutely to help her plan it, both of whom are actual natives of these men's culture.
She's not going to intimidate them by physical presence. Everyone from The Realm of the Mammoth Lords True Kellis looks like a half-giant by southern standards. Very shiny thorned metal (mithril) armor will help, but they'll all be a head taller. The pike, similar.
But they fear and distrust magic. It's a point of pride. And her job isn't to be a native, it's to get them ready to hold a line against demons.
So when she's sure they've followed the Herder's order to assemble, she uses dimension door.