I did not play those two games, and yes, Neverwinter Nights (1 and 2) were huge letdowns after playing the successors. They were as games far less cool, which Wrath is, so Wrath needs to get measured by the rest of the experience as well.

I'm not even sure Areelu is "underused", I think the uses she gets do not make enough from what she should have. I think it'd have been a more interesting story if the "twist" was revealed much earlier, Areelu takes a less distant role from the beginning, and then the time wth her was used to build a relationship.

It requries a specific type of audiance to like villain-ish characters that kill on whim.

As I said: I absolutely loved the villain they pulled off in their previous game.