Talia and Bistan are solid toons.
Completely disagree.
Talia's best use is cleansing other NS, but it's very rare that you're taking any NS squad against a team that pumps out debuffs, and when you do - well, the two most debuff heavy squads are Palp (L) and DR (L), and any NS squad is going to get smoked by a Palp or DR squad with equal gear & equal zetas.
So when you need it most, would you like to have her cleanse? I guess, but her kit as a whole can't change NS from a losing squad into a winning squad against either of those leads.
Now, I've also used Talia in the NS AB vs. that nasty encounter-4 Sidious, but when you get to higher tiers, she doesn't help there either b/c she dies from the AoE. It's Daka that saves that AB, not Talia. I'd love to love Talia. I was an early adopter of NS in my guild way back when, but she's not a solid toon if she doesn't make your NS squads better, and if you could have an all r7 NS Squad of Talzin, Ventress, Daka, Spririt & Zombie, there's no one of those toons you can switch out for an r7 Talia that wouold make the squad better.
The way I look at it, she's tied for 6th best NightSister, and that's ... not solid.
As for Bistan, well, there's simply no way that Bistan is a solid toon in any sense. His ship is a solid ship, and you might gear the toon for the sake of the ship, but he's simply not a solid toon. Period.