I've played maybe 20 games with them so far, one tournament and prepping for another one this weekend.
I found they work well for a Hold Objectives with some control style deck, their faction objectives and ploys are just so strong for this playstyle. Unfortunately, I feel this build performs pretty poorly against Profiteers, since they just get knocked off tiles pretty easily., and don't have the damage to go aggro vs dwarves. They also seem to struggle with a dedicated objectives Briar Queen due to action efficiency, and Aggro Mollog since Ghouls get ruined by the spin and the Duke gets bopped by club.
It's weird because I feel like they should be A Tier, it's just they have a very bad matchup vs all the other A tier factions. With the exception of Cursebreakers, because with the inclusion of Madness Darts they absolutely ruin the Stormcast.
They're definitely meta defining, but awkwardly I don't know if they'll win a Grand Clash, at least based on the current card pool. I'd probably put them as a solid B tier, but you can definitely sneak some huge high scoring games from people since they're both new and complex.