Yes but isn't the Veil the one thing separating the Fade and the Real world? Like if you don't have the Veil then the Fade would become one with the real world. If this was the case then it could explain why ancient elves were all mages , and why they were able to perform amazing feats of magical use (like the floating castles). Mages could draw an amazing amount of power , they could shape reality if there was no Veil. This is what the elven "gods" did. They shaped reality.
It is why Solas feels so comfortable in the Fade and why he cares deeply for the spirits that inhabit the plane.
The Veil was created to cut off the "gods" from this kind of tremendous powers. or something else transpired that could be linked to Mythals murder.
I'm sure these events are all connected.
Ashe's theory about the connection between the Well of Sorrows and the darkspawn taint is very interesting indeed.
OK, yes and this is what I get a bit tripped up over. There are a lot of little things that make this particular theory a bit confusing for me, and I'm not going to lay them out very well because I'm a bit distracted at the moment xD. First, Solas speaks as if elven civilization existed during this time-without-the-Veil, but Ashe's theory said they there were no elves, only dragons. I don't think the elves were all just dragons, that just seems farfetched and plus they are separate now anyway. When would that have happened? Why would it have happened? Doesn't make sense to me.
If the Fade didn't exist as it does today, it also seems strange that there would even be an elven Pantheon. Everyone would be able to shape reality, as people do in their dreams. Why would slaves be necessary, since one could conceivably just make the Fade do the jobs of the slaves (want water? POOF: water appears)? Why would civilization be necessary at all? How would the custom of Uthenara have evolved if there was no Fade? Why would Solas mention walking through the Fade as a child? How would the legends of Dreamers in Arlathan have come about? Why would Solas have so many artifacts that rip through the Veil to the Fade?
Keep in mind we don't have a Veil for something else that supposedly existed during the time of Arlathan: the Void. That just seems to exist elsewhere, and I think the Fade is a similar type of thing.
This theory is interesting, but I'm not convinced either. The devnote called Fen'Harel [Mythal's] eldest friend, so I'll stick to that. And to the elven gods = powerful mages theory. At least until given enough evidence to believe otherwise. 
I'm on the Gods-are-gods train. Well... gods are different. There's a crap-ton of talk about blood in DA lore. Everyone important has important magic blood. Alistair has it, Morrigan has it, elves have it, dragons have it, etc. Magic is carried down bloodlines, Qunari have some weird-ass blood thing going on. Blood can be tainted, its power can be used for magic and some blood is better for some magic than other blood. I think beyond being awesome mages, the elven gods have something that makes them more special and sets them apart from all of the other powerful mages that must have existed during that time. Because there definitely seems to be a you-have-it-or-you-don't specialness theme going on in DA.