New(?) phasing technology seen in pre-patch Legion

[JohnGabriel]

can they still follow though?

Yes.

There are two different types of phases. I don't know what to call them so will just call them fake phasing and real phasing.

In fake phasing its instant, no delay whatsoever. Its like you're still in the same instance except everyone but hunter pets are invisible. You cannot target anyone, but you can follow them, and also really weird you can trade with them, cast spells on them such as my Disc priest can still shield my invisible tank. Probably an oversight they will fix soon. I also checked and IWT works just fine.

In real phasing its just like what we are used to, for example entering an area where it changes based on what stage of a quest you are on. Wont help in this situation when its a solo quest because you're in a completely different instance and you cannot follow.

Edit: I will add that what I named fake phasing was the Khadjar quest line in Dalaran, and what I named real phasing was later in that quest line where we had to enter Ulduar.