Cassandra never does anything romantic for the Inquisitor. She demands tangible things such as romantic poems, fancy secluded spots and candlelight but never actually gives the Inquisitor anything tangible in return. She could have written a silly & sweet poem or give a nice weapon / armor (being practical) for the man she loves. If she was not the Divine, she could have either married him or get engaged to him. But nope. Not romantic enough.
Talk about making someone jump through unnecessarily arduous hoops. Cassandra's romantic relationship with the Inquisitor feels a lot like the relationship of a poor animal tamer and an animal. Hey there, get me this if you love me, but nothing for you ! Oh, you want something from me ? Nah, you are not good romantic enough !
Josephine takes the Inquisitor out on a date to the theater (or a friendly outing if not romanced), she wins Wicked Grace for Inquisitor if romanced and her family welcomes the Inquisitor as a new addition to the Montilyet family if she is romanced.
Cassandra ? Good luck expecting anything from her. Honestly if you do a cost benefit analysis, Cassandra is not a good love interest at all because she is pretty one sided.
I also think that Cassandra isn't a good love interest. It's been months that I am denying what I feel, but now I must be honest with myself. A wonderful and adorable character without doubts, but not a good love interest. At least compared to the potential she was after DAII. It started strangly with the one sided flirt options and her ignorance of what was doing the inquisitor, it got much better with the touching sex scene where she is talking with her love, but after... during the relationship... It's.. flat.. ? It's..cold ? She leaves me as my love and as her lover totally.. cold in this department, her romance leaves me cold.
I also felt she was quite..cold ? Almost dismissive compared to Morrigan who appeared really conflicted and in love despite persisting to leave the warden for her mission. ( That's probably why I want to break up with Cassandra witout wasting my time, moving on once and for all, and don't really care anymore about her once she told she wanted to do it while I would never have done that with Morrigan, staying loyal to the end )
I still remember all the tortured facial expressions of Morrigan
, how she seemed almost about to crack when my warden insisted, told her he wanted her to stay. To the point that, really affected and getting emotional, she threatened with an angry but trembling voice to leave immediately if my warden persisted to try to convince her to stay with him. Arrrg, that was so intense ! ><%¨£¨¨TT ( With burning feelings from both sides ! )
And yet Morrigan was such a strong and badass character. This is what felt marvelous with what they did with her. She has her agenda, and she is determined to follow it, and yet you can strongly feel that she regrets feeling that way, she regrets being that strong, she regrets leaving the love of her life, terribly affected. That's probably why I never really blamed her. That's probably why I enjoyed the end of the relationship.
Oh Morrigan, Morrigan, will there be a character like you again. T__T She was my Solas !!!! 
David Gaider. When I learned that he was going to write Cassandra, I was like omg, he is the writer of Morrigan, of course, It's going to please me a lot. Now, I'm just left.. cold ? Still wondering how I could feel so differently lol.