If the invasion is going on and you finish it while you have WQ emissaries available, you actually get credit towards it. For example, today I finished it after daily reset in Stormheim, but got credit for 1 world quest towards HIghmountain.
You can get nethershards from the assaults that you can either buy gear that can have a chance at legendaries, or other items like the Repurposed Fel Focuser.
You can get nethershards from the assaults that you can either buy gear that can have a chance at legendaries, or other items like the Repurposed Fel Focuser.