The whole Faerie Queens = Hecate thing is just a theory. An interesting one, but by no means the only one. And it has never been confirmed.
What everyone always seems to forget is the sheer Power of things like Uriel. He is so strong he doesn't do contested violence, he has terminated galaxies and even whole universes (WOJ). Mother Summer and Winter are at the same level, and so apparently are the Walkers (HWWBh and HWWBf). But they are all limited because of their extreme might, and so can only use that incredible power in very specific ways at very specific times. This is all WOJ. And lastly, Uriel is considered a Senior Vice President of Creation. Assuming TWG is the President and Chairmen, I really highly doubt Hades and Hecate are at the same level. There are SO MANY gods. Thousands, possibly more depending on the limits Jim has set. There are only two Mothers, three Walkers and five Archangels. That tells you something right there.
And one more thing, there is a WOJ about how the Fae are agents of those whose influence was waning in the world, and so poured a whole lot of power into them in order to maintain that influence by proxy. This hints pretty strongly that many of the old gods put their power into the Fae in order to make them much more than what they were. This goes a long way to explaining their many links to the various religions and mythologies. There was a very interesting WAG that it was Hecate who all the power was poured into, but she was split in two (Summer and Winter) and the Queens are just different aspects of the original being, and the main bit that is left is Mother Winter (on account of the fact she has never changed). But that too is just a theory.
What is clear enough, is that Hades is not at the same level as the Mothers, and therefore cannot be as great in power as all SIX Queens combined. That would be insane. He would then be stronger than two Archangels combined plus extra. It isn't impossible I suppose, but considering everything we know about Power in the series and the various beings, it just doesn't add up.
Also Hades hasn't faded, he isn't like Vadderung. He simply is less involved - by Choice partially but also because of the balance of powers. See the WOJ about sleeping deities.
Morriswalters - Mab, and I suspect many other beings have some form of Farsight or Scrying etc. This is not the same thing as being able to hear and observe every thing that happens in the dark. Not in the same way Anduriel can. Don't you think that would have been revealed by now? No. It is more likely that when she chooses, she can try and observe various events as they happen (and perhaps see into the past and various possible futures, to some degree). Vadderung, Leah, Uriel and others have all shown the ability too, and I suspect they are far from the only ones. Hell, even Harry can view events happening from beyond himself either by scrying (using Little Chicago) or even through premonition.