Favors is solid, I think he's doing as well as you can ask from him in this lineup, and he had some great nights while Gobert was out. He's not the long term solution and he'll probably leave next summer, but right now it's all good as long as he keeps working on D, making a few mid-range jumpers here and there and hustling for the occasional put-back. Plus we're seeing a nice two-man game with him and Rudy every now and then, with some excellent high-low passes that are working to perfection every time.
As for Rubio, he's not nearly the best version of himself yet, but he's doing just fine and he'll get there. He still needs to be more aggressive attacking the basket, like he was the past couple of years (that helped his scoring efficiency a lot), and he needs to keep working with Gobert on those pocket passes and lobs. Rudy doesn't have the greatest hands and their timing is still a bit off, which leads to some avoidable TOs, but the improvement on that area is evident since the start of the season, and he's taking much better care of the ball overall.