Well, I understand, that For Honor made as duel game. But it's fully advertised as medieval massive fight game. And now we have what we have.
Someone like duels, someone wait breach, and (I believe) everyone hate Dominion.=) The core game mechanic is something that not allow devs to make real medieval massive fight game. Any 4v4 mode still a duel mode. Feints are huge part of duels, but in 4v4 mode it's only a way to gunk better. Same with UB, same with parry etc etc.

So, maybe it's time to separate thouse two modes? I mean, duels it's some king of fighting game and need all movesets, feints etc. And Breach should be something different.
I think all massive modes should be way simplier. Remove indicators, UB, feints, parry and all this stuff. Pure fight with reaction block and attack. This will let you to move away from small chamber gameplay, and increase number of players to 30v30 or something around. Well, sure we could keep classic Dominion and Breach, but this will bring really new, different emotion level.

I believe a lot of For Honor players are a huge fans of Chivalry: Medieval Warfare. One of my friend just wait for Mordhau, cause he want real medieval battles with a lot of soldiers and atmoshere. Still, I think For Honor have better visual, better heroes and customization. But this game really need mass gamemode. Breach is a right step, but siege with only 4 fighter on each side sounds really stupid. Maybe start from adding bots to breach. 4 players and 6 bots from one side and 4 players and 6 bots from the other.