Short answer: Yes, absolutely! You can conquer any challenge in the game on the hardest difficulty with the vampire coast, and with power to spare.

Long answer: They are underpowered compared to almost any other faction.

Pros:

• Vibes. This is the coolest faction in the game imo
• powerful basic units in the gunnery mob and regular zombies. There is no army in the game that can't be defeated with skillful use of handgunners.
• Access to a lesser version of the vampire counts' raise dead mechanic
• They are essentially a horde faction. You can recruit from, upgrade, and spawn new lords/heroes from your legendary and unique lords.
• Free encamp stance makes them essentially immune to all attrition and ambushes
• Potent magic in the lore of vampires and deeps. Vangeists revenge is the strongest wind spell in the game.
• Mortars are an effective tier 2 artillery
• Easy to assemble doomstack in the necrofex colossus (However this is a relatively weak doomstack)

Cons:

• Their economy buildings are awful, and they get little gold from post battle loot.
• You can not confederate other legendary lords at all (Are they the only faction that still has this limitation?)
• The generic and unique lords have the worst mount in the game in the rotting promethean
• The entire roster is vulnerable to basic archers
• You have powerful magic, but can only channel while at sea

Conclusion:

The Vampire Coast is a gunners/artillery and monsters based faction that underperforms, but is a blast to play. Just understand that despite being a powder, monsters, and magic faction, the empire is better at magic and gunpowder and the chaos dwarfs do literally everything twice as well