WoW has been trash for a very long time. Sorry, I do not think there are any solid multiboxing experiences to be had at this time.

I would recommend:

Fallout 4 w/ various mods like Horizon
Subnautica
DOOM
Terraria
Divinity OS:2

Cyberpunk might be good as well. Baldur's Gate 3 should be good when it's done. Subnautica follow up is in early release as well.

Fret not my PC gaming friends. WoW is officially dead (given this news) but gaming lives on.