Just played the first scenario of Carcosa as Sefina, and I had sooooo much fun. I thought I was really going to struggle with her as I don't have a 2nd core set and the options available to her limit her successful investigations and attack options.
I don't know if I had a lucky game, but boy was I wrong.
Of my starting 13 cards, 5 were events so that worked perfectly. I also drew a Painted World in my opening hand giving me a lot of flexibility. One of the cards under Sefina was Backstab which allowed me an available 3 damage attack if I had 3 resources (and another if I spent an action to take the card back into my hand). Additionally I had an uncage the soul under Sefina, and a copy of shriveling in my hand, which I opted to pay for, but I could have played for free.
We earned 6 xp from the first scenario, so I am going to put a couple of lockpicks in the deck to help with the investigation phases, but all in all, I was impressed.
We were playing on easy, but I found her very fun.
(BTW, our party consists of Sefina, Rex, and Wendy. Not an incredibly well-balanced team, but so far it's worked very well)
I thought she would be more mystic than rogue myself, but my first game seemed to really demonstrate that she can be excellent at either as a rogue often does not need to attack to deal damage, and sometimes exhausting an enemy is just as strong as wasting actions killing it. I saved both of the other players in the first scenario by evading a nasty enemy with retaliate.
She seems very versatile and useful so long as you don't pull any straight combat or intelligence checks.
I am very much considering song of the dead over shriveling since she can't upgrade it. Maybe a couple of ritual candles too as path to carcosa starts out with 3 skulls in the bag on easy.