Such a bias isn't so unacceptable to me, but hopefully those who've gotten ganked out of the Cassandra option will find something elsewhere...
We haven't been ganked.
I am not happy about it either, but BioWare has not wronged anyone with this decision.
I'm personally okay with playing any character and orientation, but there are plenty of people who aren't so readily and prefer exclusively or almost exclusively to play a specific gender & orientation. In their case, they don't enjoy the replay value from one-gender exclusive love interests as much.
I am considering playing a male PC to do the Cassandra romance, but suspect I'd end up hating the game if I did so.
The other romances aren't quite clicking with me, but I would have said the same about Leliana before playing DA:O. I might fall head over heels for Sera or Josephine.
And if not? I've always said that BioWare is not obliged to make romances for every player and taste. If they have two f/f romances and I don't find them interesting, that's me, not them.