I have to disagree with Morrigan being a major screw-up by BW.
Me too. It was just a hyperbole.
Read Taming of the Shrew by Shakespeare, and you will have a much better understanding of why Morrigan is written the way she is.
I am sorry, but you can't expect me to go read centuries old foreign poetry for the sake of understanding an argument you are too lazy to articulate. So either you explain what exactly you mean or I will not know what you mean. That said, it also does not raise my expectations if Morrigan is really based on a Shakespeare character. If there was ever a breeding ground for tired old stereotypes in anglophone culture it would be the writings of Shakespeare.
As has been discussed on other boards, her character is actually the most dynamic by far of all the characters in the game. The fact that she does not fit the prototypical NPC makes her even more interesting.
She is dynamic. I would rate Alistair as more dynamic, but Morrigan sure is up there. The problem is that I don't think her dynamic nature actually adds anything, because the mechanics are contradictory to me. The 'Morrigan experience' consists of two parts I think. There is her role in the storyline and there is her role as a developing character. The first part is fine and makes for interesting situations and choices, but her development is incomplete. Morrigan is shown friendship, maybe even love, and she says she values it, but she does not see anything wrong with leaving my Warden alone at the darkest hour because I decline a certain ridiculous request, even though she knows her help is much needed. It is completely contradictory to the progress that has been made. There are various excuses for Morrigan, but they all boil down to selfishness, immaturity and stupidity. She is quite like Sten in this way when you, as a female Warden, have the conversation about you being female. You show him the contradiction and Sten knows that he is wrong, but he still ascribes the mistake to the world instead of himself. With Morrigan I have shown how I am not selfish and not immature, yet when she gives me a proposal to possibly save my life she expects me to betray my being. If I do not, she does not understand and reacts with selfishness and immaturity, showing her lack of progress, because she should have known very well that I would never accept such an offer. Whe becomes angry and leaves, which is a ridiculous overreaction in such a scenario. Now with Sten it is all not a problem, because he is brainwashed to not let his disposition change but he does respect you for showing him wrong, but for Morrigan this is all different because the progress is clearly shown when you befriend her during the course of the game and it all comes crashing down when you snub her absurd request.
Someone (DarkeWolf I think) stated that much of Morrigan's lines were cut from the game. If this is the case then this explains why Morrigans seems to be missing certain pieces of the puzzle in the game that would have made her character more complete.