I can answer this one.
John G. wrote a good part of Anjali's dialogue, and he did an overall polish pass on many of the side-quest NPCs in the game.
Travis wrote most of Reinhart's dialogue and about half of Katarina. He also wrote a lot of side-quest NPCs like Leona, the Gunderics, Drakomir, Fitch, etc.
The remainder of the side quest dialogue was written by the respective area designers.
I wrote the main plotline dialogues (Marten and Odo, Dapper Gent, Meisters, Jeyne, archons, etc.), plus most of Lucas and some of Katarina.