The Battle for Dazar'Alor raid sound, in theory, pretty awesome. It may have the best fighting mechanics ever and be remembered as one of the best raids of the game. However, there is one thing this raid is doing completely wrong - making people turn into characters of the opposing faction for a few fights.
In an expansion pack all about faction identity, faction pride, defending your faction's colors, having us turn into the opposing faction to kill members of OUR faction is outrageous. This is something that goes completely against the core concept of this expansion pack. It's just like if in Legion we turned into demons to kill people in Dalaran for a few fights.
The Jadefire Masters fight is a good example on how to make the fight feel different for each faction. The horde is killing some Kul Tirans while the alliance is killing an orc and a blood elf. They will look different, but play exactly the same. Maybe not all of the fights could work like that due to how their stories will play out, though.
I'm a main horde player, so I don't want to turn into a gnome and kill Zandalari trolls defending our current home. I'm gonna feel like I'm betraying my faction. I'm not gonna be excited we took those bosses down, I'm not gonna be cheering with my guild when we defeat them. Just like alliance players will have to face Jaina at the end of the raid. After fighting to rescue her, doing everything to unite Kul Tiras and having her fighting the horde at our sides, it's gonna feel really !@#$ty to have to punch her in the face. How will alliance players feel satisfied they finished the raid if they're a bunch of orcs kicking their hero's %^-?
I know keeping the raid well balanced for both factions can be difficult when you have such different fights, but, to be honest, Blizzard doesn't need to do that. Since they decided to make the story on this raid different for both factions, they should have had the courage to actually make them different. If players want to experience the other faction's story, they can - anyone can make characters on both factions. And screw "balance", the raid doesn't need to be perfect balanced and long as both can enjoy it.
"What about world's first race?" What about it? First of all, this is an unofficial, fan-based event. Not something sponsored by Blizzard. So they have absolutely no obligation to make this 100% fair for both factions. Secondly, with Hall of Fame, it doesn't matter if the horde version is easier or harder, 'cause even if 100 horde guilds make it to the hall of fame, there's still 100 spots for alliance guilds. Besides that, I don't want to sound rude for those who take mythic raiding seriously and race for that first spot, but even all the 200 guilds that make it to the hall of fame still represent a really low percentage of the total players in the game, so a raid shouldn't be tuned for such a small number of players.
Reference:
https://us.battle.net/forums/milkshake font idea