I just started Waking Nightmare today and I'm up to the part where you have to drink Vaermina's Torpor.
I drink it and get transported to the sanctum but the two NPCs who are supposed to be there talking to each other aren't there.
I can hear Orcs raiding the place, but that's it.
I re-loaded previous saves, I started the whole quest over again, basically everything that I could possibly think of.
I tried googling it but it doesn't seem anybody else has had this problem.
Any suggestions?

BTW, I play on 360.

Did you try just running to the chain that you need to pull? If I remember correctly you can't interact with anything else.

Can't. I'm stuck in place. The two people who spawn and talk to each other RIGHT after you drink the torpor don't spawn.

Really? Not there at all, huh? That's strange and I checked the wikis and didn't see anything on this.

The usual fix for weird bugs like this is to leave the temple entirely going back out into Skyrim, then reentering and trying it again. Doing that reloads the whole cell. Either that or try reloading a previous save again. I know you've already done these things but that's all I can think of.

I even installed the game to my hard drive just incase.

Hopefully the leaving and entering works. I'm only doing this so I can buy the land plot in the pale.

Nope, leaving and entering didn't work either.

Same problem

Would it be a possibility to uninstall Hearthfire then try to complete Waking Nightmare? If it works, just reinstall HF afterwards.

No, it's not Hearthfire.
I just tried it on another character of mine and it worked just fine.

Ugh, this is extremely annoying.