It was nerfed because it was always the pick in st situations too, which was too extreme. Now, with the nerf to 500%, people have some room to wiggle. Same goes for dungeons where you can’t pull the entirety of africa and then go brrr through it.
They also nerfed the other two uncapped classes quite a lot more than they nerfed Unbound Chaos. I think they’re just trying to cut down on uncapped bursty AoE in M+ and let the new gear make up for it all. Anyway DHs should still have no trouble during big pulls let alone normal AoE so just be glad we’re getting some needed ST attention.