https://blue.mmo-champion.com/topic/1103958-alliance-buffs-coming-in-81/
This was the post I was referring to btw. It won’t go to the actual post on the forums so maybe it’s been deleted?
Some time ago we made a hotfix to War Mode which enforces all War Mode shards that have both Alliance and Horde in them to have a stricter, more even ratio. We’ve been monitoring the results and so far we’ve noticed a significant improvement in “fair and balanced” shards. So much so that it’s safe to say that if you are Alliance, and you see Horde in the outdoor world in War Mode, you are a relatively even horde to alliance ratio shard. There are some rare exceptions, such as when a raid of 40 players enter a zone. It may take a bit for the “shard manager” to compensate and balance the shard.
That was in 2018, maybe they gave up on faction balance in shards since then? Or they just never fixed an exploit that let people get multiple raids into the same shard.
edit: the MMO link to the forums doesn’t work, but the actual post is still here: Alliance buffs coming in 8.1 - #41 by Ythisens