They don't need "chemistry" in the sense of being able to work right next to each other to write songs.
They've never done it that way. 99% of the songs, except stuff like Tumble in the Rough and Vasoline, the DeLeo bros. and/or Kretz work out almost all of the chord changes and ideas before Scott does anything. AFter that, it's only slight changes to account for Scott's vocal ideas (you can see an example of this at the beginning of the extended version of the Big Bang Baby video from the Thank You bonus DVD. The band plus O'Brien are listening to a playback of the verse, and Weiland and O'Brien are showing the DeLeos that for Weiland's vocal, the riff needs to be played one more time before going into the chorus. Notice when they're singing along with the track, Weiland needs one more time through the riff to sing the last "How the story really goes / So we all just hum along" before the chorus.) This is the most collaboration they have.
For the most part, Weiland respects the DeLeo's song crafting, and they respect his ability to take it to the next level with a melody and lyrics. And they do these things mostly apart from each other. They've even talked about the fact that Weiland usually is never at the houses they record at unless he's recording his vocal parts.
As far as VR being great, well, they were pretty good. But, they were limiting for Weiland. Actually, STP are too, or he wouldn't do solo records. But STP experiments a lot more, and they grew up together. You can't bottle that, and usually, it doesn't go away. So to say that VR had this chemistry right up there with STP, IMO is false.
But opinions are like...well, you know lol.