Yes, I liked Jool later on, too, which is why I suspect the basic problem was that the writers hadn't yet figured out what they wanted to do with her when creating this episode, beyond "Not Zhaan". Now sometimes that doesn't matter - see also all the examples in various shows of one-shot characters who were never meant to come back but did because the actor was that good or the chemistry was great or the success with the audience was beyond anything they'd hoped for. But here, it's noticeable. Still, they fixed it.

Harvey: absolutely, this was a stroke of genius on the part of the creative team.

AND wtf was up with him and Aeryn?

I mean, I guessed back in the day he started to fixate on her because Zhaan died for her, plus who knows, in wacky sci fi terms perhaps Aeryn ended up with some of Zhaan's life energy/aura or whatnot. Or maybe it's because Aeryn died and came back to life, and Stark, who is after all an energy being and one who professionally helps dying people on the way is fascinated by that.... but whatever the intention, on screen it just came across as creepy and stalkery, and did him no favours in terms of characterisation. Why anyone thought this was a good idea to waste screen time on, I don't know.