Alright.
Yeah... I won't get into the political issues there but...
Now, this is just me, and I don't know if I'm just an insensitive psychopath or what, but the original story idea would have been hilarious!!!
I get that people do/might/will get offended at such a scenario, however...
1. This is a fantasy game. It isn't real. Rape is a very real thing but... what are the odds of having sex with somebody possessed by a demon in real life? None.
Going on that, the idea of rape in this scenario is a bit of a grey area itself. Initially, you consent to doing the deed with Leliana thinking that it's Leliana, you get your rocks off and that's all good but... then you find out it was one of those disgusting envy demons, so the idea sickens you, you get a bit freaked out, etc. But during the time of having sexual relations with fake demonic Leliana, it's safe to assume you were enjoying yourself.
Hypothetically, if I slept with a serial killer without knowing they were a serial killer, then later found out... can I say it was rape?
Yeah... nah. Well, I personally wouldn't anyway.
2. I fail to understand people who get so angered by these political issues that have manifested in the game. Just seems somewhat hypocritical to preach good morals when a majority of the game consists of killing people... on top of that, the game still features some borderline controversial scenarios. Take judgment in a box, for example. It's clearly making fun of the fact that you kill Florianne... and believe me, I'm not alone in just about peeing my pants with laughter about the situation, so what does that say? 
It's important to remember that more often than not, we actually have a *choice* whether we want to be borderline psychopaths in the game, or saintly social justice warriors.