I'm going to go out on an 'unpopular opinions' limb here and say Alison Pill was definitely the weak link in the cast as Jurati. It didn't help how they wrote the character--one Tilly is more than enough, guys. Maybe it was more of the writers' fault, but I don't feel like the actress was up to the role. For example, her anguished face looked more like acute constipation. Imagine Mary Wiseman in the role! I think she would have knocked it out of the park.
Strongest cast member besides JL? Definitely Auntie Raffi, honey. Michelle Hurd killed it. If the writing had been up to par and the character had been given more space to breathe, she could have easily taken over the show from Sir Patrick. I went in expecting to dislike the character based on what I had read, and she ended up being my easy favorite. She's the one character I could see fitting in on my beloved DS9 without a hitch.
The rest?
I thought Santiago Cabrera did fine with what he was given. The holograms were a cute conceit and he clearly enjoyed playing each one. The show needed a Han Solo type, and he played it well. Another example of a character that could have been so much more with five or six more episodes.
I liked Harry Treadway as Narek, damn it. If the writers hadn't completely dropped the ball with him in the last two episodes, he could have had an epic heel/face turn. But he disappeared in Part 2, so...oh well. Must have decided to stay on the Borg cube, looking for his sister...
...who was terrible. Peyton List was awful, and the character she played was awful. Go watch Youtube clips of Marc Alaimo and try again. Writers, throw away the "How to Write Cardboard Villains" guidebook.
I thought Evan Evagora did well with what he was given, which was not much. I would have played up his relationship with JL a hell of a lot more, but the writers seemed intent on rushing the story through in ten episodes (and practicing some truly horrific time management along the way).
Isa Briones? Absolutely enigmatic and haunting as Dahj, a big wet fart as Soji. Again, I truly feel that was the writers' fault as opposed to hers. She did a good job as the evil sexbot, too. I hope Soji gets a personality upgrade next season, because Briones deserves it.
Jeri Ryan did a serviceable job as Seven of Nine. Nothing extraordinary, but it was good to see her again. Jonathan Del Arco was amazing as Hugh, though. Definitely the character with the most heart (sorry, Elnor). A shame the show felt the need to kill him off.
Frakes and Sirtis? They both did a fine job, and Sirtis was surprisingly good (heartbreaking, even). And where the hell did Lulu Wilson come from? She did such an amazing job. Just the way she acted with her eyes alone...that kid has got to be going places in Hollywood.
There's more, but those are the ones I wanted to touch on the most. A generally good cast that got completely screwed by some rushed, wtf-level writing. Such a waste. But I'll be glad to see them again in Season 2.