To be completely honest I thought the most recent St Vincent album was the best record she's ever made. Loved how her experimental side and her pop side came together in a way that felt accessible while also not being a sell-out. and she somehow brought out a lot of the emotion that I felt had been missing from her music pretty much ever since her debut. I'd probably peg Actor as her weakest record. It's the album that made her big so it will probably always get a lot of praise from people, but only the singles really still hold up for me.
Neko Case is maybe in a slump. But she's always been consistently decent even at her worst. I thought her new album was fine, but I only spun it twice. And certainly nothing stood out to me like the songs on "Fox Confessor" or "Middle Cyclone". So I guess you're right, I suppose that counts as a slump.
I was going to suggest maybe The New Pornographers, since their recent albums have been weaker too. But they're also kind of a consistently average kind of band. Their new album was really only their worst album by default cus there were no Bejar songs. AC Newman isn't nailing the immortal pop hooks like he used to either, but they're still fairly reliable.
NP Can Delay 1968 - Can are a great band but damn Mooney sucks, all of these songs should have been instrumentals.