snkboarder: Hexxat is my least favorite addition to any of the EE games. As usual, there is only one Dev-approved outcome and anything else leaves you with a pittance of XP and minimal loot.
That being said, the lack of continuity between how you engage with her in SoA and ToB is, like a lot of the new EE content, not quite thought through.

Background:

When my party first encountered Clara in the Copper Coronet, it seemed like she was going to have some sort of quest where you rescued her from evil and then she would join your party and be normal again. You take her into your party, you gear her up, you go off to do her quest. You end up spending a fair amount of time with her, party because she walks so flippin' slowly.

What we got was this bizarrely heartbreaking cut-scene wherein Hexxat murders her in front of you and then turns to you and goes, "Want to join up?"

I actually said out loud to my monitor: "What? NO! You just killed some poor girl right in front of me, you ******!" I normally play as a Chaotic-Neutral character because I think it's the most challenging to maintain balance while also being unpredictable— I went 1000 percent Lawful-Good as a gut reaction and slaughtered her. You get, basically, nothing for that. And on top of that, it isn't even an interesting fight. A few arrows and a sword whack and she dies. No mist, no coffin to stake: Nothin'. The Devs were expecting you to jump for joy as you take this murderer along with you. People seem confused when you don't, because if you do, you get a Bag of Holding. This game makes it very clear that vampires are evil and not good for you, your party or the storyline in any way, shape or form and then the EE Devs 10 years later expect you to wipe your memory and go party with one. If you don't, it's not even worth pursuing the earlier questline unless you're an evil party, of course, in which case this is a very boring role playing opportunity, for you. Except that you don't get the choice to be evil. It's not like you can save Clara or sacrifice her for Hexxat. It's like, "Be evil...or don't get a bag of holding!"

Even the smallest amount of effort from the Devs could have made this a fun quest. There could be two major lines with two options: One is you kill Hexxat and save Clara, getting her in your party and the other is to sacrifice Clara to gain Hexxat, which is fun for evil parties. Because it's a choice. There could also be neutral outcomes where you break Clara off from Hexxat's curse, but it weakens both and you end up with neither in your party. Or whatever. If you, reader, spent more than five minutes on it, I bet you could create something infinitely better than what exists now. This reminds me a lot of Neera/Rasaad/Safana-SoD "choices" which were either A) Do what the Devs want or B) Get nothing. And at least make Hexxat a fight. Even evil parties like slaughtering vampires!

And even then, it's not like Hexxat is this amazing character you just can't live without, so you're willing to forgo roleplaying to get her. There are far more useful cahracters in the game for almost any party build.

The current lameness:

I slaughtered Hexxat, as mentioned previously. Then I roll into the tavern in Amkethran and low and behold, there she is chilling in the back room. When you talk to her, she's like "Hey, it's you." And your responses are "Long time, no see..." She should be like, "Oh, you brutally murdered me after I brutally murdered that girl." And your response should be, "Hey! Didn't I kill you?" or "DIE!" and this time, give us a chance to stake her coffin. So what did I do? Kill her again. Just on principle. To spite the Devs. Why? Because neither time you can kill her does she create a mist that moves toward a coffin. She just dies like an everyday newb. So she shouldn't be coming back to life through vampiric magic. Also, she's a crappy character and her quest is not fun.