Re: Romances

EA did not * up anything. They did not develop the game. BioWare did.
In addition to that, if you're playing a male and try to flirt with Sera, she makes it clear from the very first attempt at flirting that she's not interested. ("I think I'll enjoy having you around, Sera. I hope you'll feel the same." - "Pfff! Not even!") If you keep flirting with her, she will get more blut about not being interested every time (until she actually says "your thing is not my thing"). I really don't see how you could flirt with her all the way through without realizing that she only likes females. It is evident that the developers tried to avoid this situation you're in through her dialouge and I'm sorry for you that you ended up in this situation anyway, but that's neither EA's nor BioWare's fault.
If it comforts you, you won't have to romance Vivienne, since she's not a romance option at all.
Dorian and The Iron Bull are your only choices left if you shot Cassandra and Josephine down. Both of their romance routes are great so if you do play for the romance aspect of the game, you can still have a great time with these two possible love interests (I personally would recommend Dorian's romance).
The only thing you can do if you insist on a female love interest for your Inquisitor however, is to go back to an earlier savegame or start anew.