I'm honestly not sure that this will get nerfed at all. The crux of WP Speedruns is taking extreme risks in the name of doing it more quickly, not exploiting bugs and oddities in the game itself or avoiding half of the monsters in the dungeon. Sure, the structure of the dungeon probably never intended for us to aggro every enemy before the dungeon's first boss at once, but more power to you if you can actually survive. Even the boss barrier trick is a calculated risk: The boss fight can get dicey if mobs actually enter the arena with us, and the Tank is fending off damage from more than just the boss for that first 15 seconds.

That being said, I do think it's odd for monsters to just spontaneously ignore the party when a barrier pops up in front of them. I think it would be hilarious if they still tried to chase the party and immediately swooped in for the kill once the boss is dead