My impression is that Quentin's infatuation with Daphne is largely, if not solely, of supernatural creation. He's just not acting like the Quentin-on-the-chase that we're used to seeing. As for the isolation and the dead-end non-role, he may still be recovering from Amanda's death.
Well certainly, uninfluenced, on-the-prowl Quentin wouldn't be pursuing a
ghost, so that's proof of supernatural influence right there. We do see some struggle going on though (maybe more so later), so he's influenced but not totally controlled. I don't know if Q's isolation and possible century-mark crisis make him more susceptible to influence, but it seemed interesting that they might.
It's hard to imagine pining for Amanda like that, but it's certainly what he's supposed to be feeling...