This sounds a lot like the awakened invasions, except a bit more fleshed out? With probably a bounty-like boss at the end. I hope it's interesting (and challenging) if they plan to make this a cornerstone of the new legendary armour and the expansion.

So these new activities will be available to players without the expansion right? they just won't have the bonus of closing the rift for extra rewards?

Rifts like in RIFT ?