i asked PW just 3 hours after the DLC hit the streets, he still told me "Spoilers". If it was his intention for it to be a crystal clear proof why wouldn't he confirm it ?
I concede one point to you. It is possible that Solas killed Felassan. It is possible that Solas was written that way at the time TME was written, then PW got to write Solas on the game and add the romance and changed Solas. Or kept Solas as planned: changing as you see him. I just don't think so.
But today's Solas, the one we saw in trespasser, fully developed by his author, is not the same as that thing on TME. And I know PW is a tricky devious genius. So I'm pretty sure what we will find out is going to be surprising.
I think the problem is, what Cole says about it and about a dumped Lavellan connect to Solas and no one else.
Solas: You cannot heal this, Cole. Please, let it go.
Inquisitor: Perhaps Cole can get a better answer from you than I did.
Cole: He hurts, an old pain from before, when everything sang the same.
Cole: You're real, and it means everyone could be real. It changes everything, but it can't.
Cole: They sleep, masked in a mirror, hiding, hurting, and to wake them... (Gasps.) Where did it go?
Solas: I apologize, Cole. That is not a pain you can heal.
In Trespasser Cole says:
"His friend had to die. Because he thought they were people. A slow arrow breaks in the sad wolf's jaws."
And the wolf part is a dead giveaway. Later in Trespasser Cole calls Solas a wolf.