Naysayers.
Horror lists are completely viable, but require you to really have a firm understanding of positioning, and are very reliant on a single model; The Hanged.
Because of Seamus' insane engagement range and the Rotten Belle's insane Lure Range, and the incredibly reliable protection of the Crooligan (As well as Creepy) you won't really have a hard time getting your bubble to your opponent, safely and reliably, regardless of what theoryfauxers say.
I suggest trying out a horror list on your own before you get talked out of it.
Keep in mind though, a well-oiled Horror crew is incredibly unfun to play against. You can create an enviroment where any easily-targeted models are easily recreated, where any failed movement action leads to Paralyzed, and where nearly all of Seamus' heavy hitters are both hugely offensive, and nearly untouchable.
The basic mechanics of a Horror List are
1.) the Hanged's Inevitable Terror (I think that's what its callled) that removes any immunity to Horror Duels, even the immunity granted by succeeding in a Horror Duel,
2.) Seamus as your engager with his Spectacular Infamy upgrade. This makes his Terrifying effectively Terror 14. Leap him near / on top of the enemy's sniper type models. With them locked up,
3.) Rotten Belles lure in the runners. If you've got Sybelle, Bleeder Lash + Not to Banged Up makes your crew a flytrap. The models are pulled in at a greater walk than they can leave with, and once you get them into your horror bubble, they're totally screwed.
4.) Crooligans for The Mist primarily, and Creepy secondarily. The Mist gives your crew a greater chance to resist the snipers that can undo you crew until Seamus can wipe them up.
5.) Bring at least 1 heavy hitter with Terrifying, my personal favorite is the Dead Rider, but the Rogue Necromancy or Killjoy work well. In smaller games, (35 or less) the hitter isn't as important.
The reason I prefer the Dead Rider is because of his Drag Along. You can engage a target, inflict decent damage, and then pull them into your bubble.
Your absolute minimum point investment is around 15, 9 for a Hanged, 4 for a Crooligan, 2 for Seamus' spec infamy.
It can be tricky to learn at first, but once you understand the basic themes of a Horror list, they are devastating. Don't let the circular logic of this forum dissuade you from playing how you want.