You are right, tearing down the veil will probably not help the dwarfs. Something still doesn't seem to fit. Isn't Andruil bringing back the blight from her hunting in the void? Maybe during the war against the Titans she infected one of the Titans with the blight? Or during the mining? Or do we have a reference that the blight was always there with the Titans?
Though gameplaywise I have to admit that facing a blighted Titan would be awesome!
Or having a non-blighted Titan in your party. A girl can dream.
There is no reference anywhere that I know of the origins of the Blight, no. My guess is it's either always been there, or at least predates the Evanuris/Titans war. If the Titans are alive, maybe it's a sickness of the song they produce. Something that comes naturally as the harmonies of the song warp with time and distance. Who knows. Another theories could be that the Evanuris created the Blight first as a weapon against the Titans, but although I first thought that might be the right answer, I tend to doubt it now.
As for the void, I admit I have no idea what it is. The inside of a sleeping titans maybe? But, the one we visited was beautiful, not anything I'd call a Void. The inside of a corrupted Titan then? Perhaps. It would explain how Andruil brought the Blight back from it. And the codex says she went there to hunt. What kind of strange creature could inhabit a void-like blighted Titan I wonder...
As for the last bit, I'd love being able to converse with a Titan directly, but I think they're way too big to actually move around. Hell, they seem to be a empty space surrounded by sentient Stone, so they're unlike any other living creature we've seen in Thedas. I'm uncertain they can actually move the way we understand it. A connected dwarf like Valta though might become a complanion. Again, I'm not sure how that would work as a dwarf going to the surface seems to lose all sense of the Stone very quickly, so a connected dwarf wouldn't be able to stay connected if they left for any length of time. I don't like the Deep Roads enough to spend an entire game underground lol.