I have to agree that the romance was quite lacking in depth with this one.
1. Aerie's romance not deep ? I have to disagree. Just to get things right: Aerie has (ToB included) about 60!!! so called "love talks". I builds up slowly and is deep for that very reason. Additionally, you can end the romance at various points with the wrong decisions. In comparison: Bastila in KOTOR has about 10 such dialogues.
2. It's pointless to discuss percentages. 10%, 20% or 25%... that's no what really matters. What matters is: Friendship comes before romance. That's why it's important for the romance to build up SLOWLY to be realistic.