devtrackers.gg
I didn't decide eod balance changes, but I do play the game a lot and provide general game feedback around my own play, unbiased as possible :
A) I don't see how 5 man mirror comp would be worse than 10 man mirror comp. There is always going to be best in slot options for very specific uses, even if they are super close and "balanced" in various ways for various occasions. I'm not necessarily referring to how the game is currently, but more a theoretical situation comparing a 5 man mirror comp to a 10 man mirror comp.
B) There are many options now in comparison to the past. Beyond that, I don't see exact mirror composition being important to my own gameplay. I play both arguably strong stuff and also arguably weak stuff, regardless of whether I'm finishing cm main clears for the week or for a learning boss for hours. I don't base my build wholly on just how powerful it is, or the builds of people around me.
C) The benefits and potential of 5 target over 10 target, to me personally, seems so good in comparison even if it was the same 5 duo specs every raid.
D) I see shaking up the meta and what is the most powerful as potential content and good healthy gameplay in and of itself.
E) Focus on hype and the potential change brings. EoD is coming with big changes to the game in a multitude of ways and its going to be outright amazing.