Love code2501 thoughts, they feel pretty close to what I've been pondering.
Few rambling notes, rampant speculation and happy fangirling ****** to add:
Wardens Keep? enters a new thought that the 'blight' is very much alien and different to the Fade I think. Hence the mage's continuing experimentation.
To my thoughts along codes line...
Elves used to 'walk/exist' mostly in the Fade. Reality for them was like a living dream, hence their magic and ties to the Fade.
Dwarves are their polar opposites. Bound to the earth and completley unable to touch the Fade. However their very earthbound nature allows them to work 'lyrium'.
..Does something in the earth/ground make Lyrium or does the earth act like a catalyst, pulling raw magic out of the air? and condensing it into a physical substance.
Possible idea of elemental polar opposites here. Fade = Plane of Air/Magic. Hence anything that's related to the Earth is foreign to it?
Humans are neither elf nor dwarf, but something in between, hence their ability to touch the fade in our dreams.
Old Gods: Maybe not Fade Vessels but instead perhaps something else that resided in the ground before the elves came about. Following the planar elements thought (possibly to breaking

) If the Fade plane has native Spirits, why not the Earthen plane? Perhaps ancient entities with incredibly alien minds that are constantly opposed? We haven't really seen the most powerful creatures of the Fade, we know that. There are those statues everywhere in there of the hooded man with the spike/tentacles rising from his body and arms. What is that?
because its something that's apparently happy to help test/play with mages and smart enough not to draw attention to itself like the lesser demons do.
Elven ruins: I thought those were the remains of Arlathan. Elves and humans like side be side for a short time ( elves-who knows how long for humans), tho time could warped memories, so what now looks like elven and tevinter, may instead be pure elven? If Arlathan was the great prehuman culture, wouldn't it make more sense for humans to copy the elves architechture, at least initially.
Dragons: If we only seem to see newborn, juvenile or flying/Breeding females, Where are the males? Why so much time between sightings?
Blood Magic: It seems to be woven throughout so much history.
The Dalish keeper used it to create the curse. The Grey Wardens use it to control the Taint. The ancient elves and Tevinter mages used it. The Templars/Mage cirlce use it as a means to track rogue Circle mages. Perhaps Blood Magic is a 'devolved' form of magic. Not using pure Fade essence/power, but something else, with a very physical medium of living blood essence.
...Blood contains Iron, which makes it red and an element binding it to earth. The power of Blood magic is its ability to draw from more than one source ( the Fade) and instead from two sources. Fade and Earth? The two power sources being opposing, is why blood magic 'warps' its users?
...out of ideas for now.