Krile and Sphene sound more similar this time because Krile forgot how to do the voice, doesn't care, or the studio lost the presets they used to get her voice that way. I could see her just not giving a shit, since the rest of the team has clearly started phoning things in and I think Sphene's VA is still having fun with it.
I'm basically of the opinion that the old cast shares the same disdain for the direction the entire playerbase has, and doesn't see a point to try if they're anyways second-billing to the most obvious nepotism-baby in the world, Wuk.