That plus backline area stun/blight. Incision is decent and gives a bleed option. Disorienting blast adds shuffle and corpse clear. Overall really versatile, so far I havn't encountered a situation where I actually regretted putting a Plague Doctor in the party. Even in Warrens/Weald/Courtyard she's still fine due to Incision, which just shouldn't happen.

In dancing terms Vestal is the anti-HWM. She's not a dancer herself, but can work very nicely in dancing parties. As you know there's basically two vestal setups, backline and rank 2. The CC trinket set adds bonuses to both and a dancing party is the way to capitalize. Vestal herself never dances, but you can play e.g. a Shieldbreaker in a way that manipulates Vestal position between 2 and 3, depending on what you need out of your Vestal skillset atm. Now arguably this is unnecessary, since you'd usually just put her in the backline or rank 2, give her profane/sacred scroll, and she'd be perfectly fine - probably even more effective for less work. The pseudo-dancing Vestal ist just a fun option to play her.
Antiquarian less so, but there is Get Down and afair many of her skills work from a multitude of ranks. I've not found a way so far to really utilize her in a dancing setup, but I think it should be possible. Since you like Highwayman you can also pair her up with him, both in the frontline. I wouldn't call that a dancing party, but it's an option.

I have to disagree here. Grave Robber adds blights, buffs, debuffs and stuns. None of which are particularly good, but it's some versatility. Shadowfade also offers backwards movement and gives her some dancing flexibility. Highwayman has damage and that's it. And even that only as a lone dancer. And not to ranks 3&4. In fact, Highwayman has nothing to hit the backline without damage penalties, unless you run a marking party or force him to guard with an Antiquarian to utilize his Riposte more. If you want to attack the backline, Graverobber is a lot more potent.
I like both, but for very different party setups.

Yeah, but what's the problem?
Abomination can deal with rank 3 fine in human form and in beast form absolutely annihilates the front ranks. Ranks 3 and 4 are not that dangerous that your entire party has to deal with them asap. So you could, for example, stun the backline with a Plague Doctor, while Abomination takes out the frontline and conveyor belts 3&4 within reach, or shuffle the backline into range.
The CC trinket set also suggests shifting the Abomination from rank 2 to rank 1 with Slam to fully utilize it, so there could be a neat dancing option, though I haven't experimented with that so far.

This is a bit surprising to me, I actually thought she's plenty viable already and with several mechanics no one else can provide I'd never have called her low impact. Exceptional dancer, decent blighter, bypasses guards and protection, great AoE, pulls, destealth, block, debuffs for days ... imo there's a lot to like here.

You're not going to get any arguments from me here. He's a star in the Crimson Court, but that's about it. But then again, damage isn't his job.

I don't really get that tbh. The game isn't really difficult, it's fine if 3&4 survive the first round. Ideally you get a few surprises, too, so I don't think enemy ranks are that drastically set in stone. There's lots of ways to deal with the backline, too, and Highwayman didn't exactly shine there pre-patch, either. You have to deal with the frontline sooner or later, why not utilize the guy that hits there like a truck?

Those are cool parties, but there are many neat party compositions in the game. Shouldn't be too difficult to adapt. I'm also a bit surprised, because if you want to deal with the backline as efficiently as possible, this doesn't quite compute. Holy Lance and Iron Swan are great here, Vestal and Highwayman less so, and bringing a Leper for Intimidate ... if there's a straggler with a few leftover HP that you really need to get rid of right now, I guess it's an option. To be honest, I'm not sure how well Highwayman works in that setup. Duelist's Advance's Riposte is active for two turns, meaning you only need to use the skill every other turn. However, here you need to use it just to reset your Crusader/Man-At-Arms, and in turn you get a -20% DMG penalty and a lone Riposte in the backline without guarding, and you practically eliminate Bulwark of Faith and Retribution from your options. I guess you could just stay stationary with Highwayman on even turns, Crusader and Man-At-Arms have enough options for rank 2. But what's your Highwayman's role in that case? Rank 3 cleanup with Grapeshot Blast?