This is from a wowhead article. Can’t link so just pasted the info here. I’m only 79 so I can’t speak for lvl 80 but im wearing my full conq set from dragonflight and my 4piece tier set ofcourse and rn i am absolutely wrecking people in arenas and bgs. Most are going in wearing pve gear from the new content. Here is the info:
Looking to increase your power at level 80? Sometimes, the best way forward is backward. Dragonflight Tier Sets are still active at level 80, which means that by giving up a small amount of stats, you are able to increase your character’s power by around 10 to 15%, depending on your spec.
It is unsure if this is intended or not by Blizzard, as Dragonflight Tier Sets will likely be the best-in-slot option until you’re able to get full Champion track gear for some spec.