Yes. I put down the Vatta's War series to read Hunters in the Dark, and in hindsight I felt that I should have just waited to read that turkey.

What did Vale do that made her badass?

I don't remember her introduction, but she was injured during the Mayhem's crash. The Huragok that the Elites brought with them fixed her up, and when one of the Spartan IVs came to visit her, she accidentally knocked him to the ground. That got people speculating that the Huragok had somehow augmented her while doing repairs, until they remembered that this is a Spartan IV we're talking about.

Sometime around now, not sure if it's before or after the Mayhem set off, Vale spent much of a chapter chatting up one of the Elites. She chides him for being too tense, and asks him to sit down. He replies that sitting down would leave himself unguarded.

After that, everyone left the ship on foot to find the Ark's control room, and find themselves beset by two packs of feral animals. Vale distinguishes herself during the fight, but that's not particularly impressive. Let's be honest, not!Wampas and Blind Wolves are animals. The company has two Spartan IVs, two Elites, and most of the soldiers are armed with a rifle that can fire 7.62mm NATO bullets on full auto. Not helping is the fact that Peter David could have novelized the scene in Halo 2 where the Chief gave the Covenant back their bomb, and make it trite and humdrum.

Anyhow, it doesn't take long for the company to realize that Vale's gone missing. Seems as if the animals have spirited her away, and she spends the rest of the novel chatting with the Ark's Monitor. Now, a Monitor that has gone off it's rocker and is thoroughly pissed at the various species in the galaxy for wrecking every Forerunner artefact they come in contact with could be interesting, but it depends on the writing. And the writer. This too was an opportunity to show how smart or witty or generally awesome Vale is, but it was just boring.

And, finally, she fought that Spartan's brother. Could have been a badass fight scene, but...
-As I said, Peter David can't write combat and make it interesting.
-I was still scratching my head over why the Monitor would lengthen the guy's arms instead of capturing two humans. Or firing up the cloning machinery in the Ark and making more Humans.
-The description of the monster-that-was-once-a-man didn't feel like something out of Halo. It felt like a description of a cheesy monster-of-the-week from Dr. Who.

Ding dong, the Monitor's dead. Went down like a chump. I think the last scene with Vale had her talking with that same Elite, who sits down for the conversation. Cue the (rated PG) fanart.

Vale's character can work, but she was handed to an author who... Peter David's strengths just aren't in prose writing. 343i is trying to astroturf Osiris Team, and they're making some of the same mistakes that Disney made setting up the Marvel Cinematic Universe for the Avengers. So Peter David has to integrate Olympia Vale into the story and make it clear that she's Spartan material, but he doesn't really know what to do with her.

The end result: We're told that she's a top tier martial artist and a master linguist and an expert on Sangheili culture, but the only payoff is a dollop of romantic teasing with Usze 'Taham. Seeing as how she and Buck are the only interesting members of Osiris, she deserves better than that.