The Glaives were just overpowered and did a lot more damage than the Airship, Demolishers, or Bombs did.
And by sheer coincidence, it just became the Alliance’s go-to strategy to grab the Glaives, so the Alliance won.
The changes Blizzard have made to Isle of Conquest since, they have definitely made it more balanced overall. The Glaives are now more comparable to the rest, which is good. But those changes have happened at the expense of the Alliance’s dominance. Now the win-rate is probably closer to 50/50.
That’s a thing as well, right?
If you look at that old data, there are 3 outliers: Alterac Valley, Isle of Conquest, and Strand of the Ancients.
To Blizzard’s credit, they have addressed all of them.
Isle of Conquest is a balanced battleground today. It just is. Solid job by Blizzard there.
Alterac Valley is better (because Blitz was litterally the simplest form of gameplay imaginable), but it heavily favors Horde now. They can zerg faster than Alliance, and they can defend easier as well, because of the Iceblood choke.
And then Strand of the Ancients was removed. Why?
Because Blacklisting, right? As Alliance you didn’t really have any blacklisting preferences. But as Horde you were definitely looking at the 3 Battlegrounds above as the ones you didn’t want to get into. So Horde players used to Blacklist 2 of them and complain about the remaining!
As an Alliance player you could sit in queue for Alterac Valley for a really long time, because most Horde players had it blacklisted. So whilst you had a high win-rate in Alterac Valley as Alliance, you didn’t actually play a lot of Alterac Valley games. The Horde simply avoided it.
Like I said, there have been more. I know there was one in 2016 or 2017, I think, on the US forums. It was during Legion if I recall correct. And it showed the same.
And I also recall one from Arenajunkies, but that site is no more. Not sure when it was from.
But I’m not going to spend more time on google than I already did. I feel like I’ve presented enough to make my point already.
Regardless, the most recent battleground changes Blizzard made were implemented in 2018. You can see them here:
https://eu.forums.blizzard.com/en/wow/t/feedback-epic-battlegrounds/4904
And those changes, along with prior ones, have generally been good for the Horde.
I personally feel the evidence is rather conclusive.
Anecdotal evidence is solid enough on its own at this point as well, because you’re definitely not experiencing a 92% win-rate in Alterac Valley today as Alliance. Or an 88% win-rate in Isle of Conquest. And that 72% win-rate for Horde in Strand of the Ancients? Well that’s just gone now, isn’t it?
Alliance players should have been laying a consistent smack-down on the Horde in all the other Battlegrounds in the recent years to have an overall 50/50 win-rate today. But there’s nothing that would indicate that the Horde has lost their edge in Arathi Basin, Twin Peaks, or elsewhere. They didn’t for years in the past, why would they today? If anything, the Horde side just creeps toward more dominance, slowly but surely.