It's been like, a few years since I've played, give me a break
It was never useless when OF first came out either, it was just fallschrimjaeger were too good at the time so the other doctrines got underplayed and the gameplay for tank destroyers or scorched earth didn't start to develop until the fallschrimjaegers got toned down.
Back on topic leave mirrors in because I want to be able to do BO1 rounds in tournaments.
With regards to DoW2, mirrors weren't really mirrors because of the commander choice which gives you different abilities to spend red on and also the commander them self which greatly effects the game or you had players like who had a pocket faction they used when they didn't want to play mirrors since you had 6 factions to choose from.