They were lumped in with the Witch Hunters, but you could use them without Inquisitors...not so much the other way around though. At the same time, the Grey Knights were lumped in with Daemon Hunters, so it wasn't unfair.
Hmmm...one example being Daemonifuge?
Yup, I was complaining about that when they happened. I think the WFHB Storm of Chaos thing was worse, the fluff basically said "and the fate of the world was about to be decided, but everyone got broed at the last moment and went home". Also very annoying as there was mention of stuff happening in Cathay in the far east...no models for that so anything goes, but they didn't bother.
Before that, Albion was about to decide the fate of the...nup.
Real shame, because they had some quite decent fluff leading up to it.
Eh, I liked the way they did the Dark Eldar myself. They were only briefly hinted at before they came out, though there was mention of piratical and savage eldar before.
But, they are added to the fluff without changing much, they were a minor faction, the webway meant they could be anywhere in the galaxy. So you could care about them if you wanted to, or ignore them if you didn't. GW didn't ram them down your throat, thye didn't alter your armies fluff.
The Tau...they undermined two of the biggest parts of 40k, that progress is just impossible and everyone is a bastard. Now you've good hippy commies who build new stuff and aren't that nasty. And they only live in a tiny area of space, but GW kept blathering on about them over and over.
The Necrons...suddenly they are the most evilest thing evah! and everyone has always known this, just nobody said it out loud. Meh...and by the time they changed it to tone it own, the fluff had settled down again so it again didn't work.
Nids are quite reasonable if down well, only, like everything else, they usually aren't.