I've just started playing a halfling ranger, and I've noticed some class-specific dialogues, including the one Dez mentioned above. I was half expecting a response like that thanks to the classic Dracula line.
A couple of them have been helpful, but nothing really noteworthy so far.
On a side-note (about race-specific dialogue options), I was suprised at how many halfling options there were (at least in the Grove).
I played a warlock on my first play through, and I don't recall many specific dialogue options for them, but the few I do recall were not something my character would say. They did sound arrogant/boastful, and I don't think they should assume that all warlocks would be like that. I think it would be helpful if the class-specific lines were functional (i.e. based on their abilities/knowledge) rather than indicating a specific personality.
For my druid, there were at least a few options that seemed appropriate (e.g. stuff about cleansing the land), but I didn't like that their tone was overly formal at times (in contrast to the other options). I feel like that would be less likely with someone in-tune with nature and less urbanised.