Even "Seven Deadly Zens" which I consider to be Shaw's best post-Styx album (including Damn Yankees) I feel could have been a lot more powerful if the creative influence of Dennis and JY had been present.
I completely disagree with this. 7DZ is the best solo effort of ANY Styx member, ever. Tommy didn't need JY, or Dennis (or Ted, even on Ocean). 7DZ absolutely blows away all of Tommy's previous solo material...7DZ made it seem like all Tommy and the label were concentrating on were pop and top 40 'hits'.
Dennis and JY's solos are mostly forgettable, and have been basicaly forgotten. JY's videos are good for a laugh and Desert Moon is good in a nostalgic sorta way...But, that's about it.
As for your 'theory' about tension in great bands. I somewhat disagree. When the members have fundamental disagreements on where to take the band and sound it seems to mean the band is about to break up - not that there is going to be a tremendous album coming from the band. So, you end up with a mediocre album where ONE member dominates and the influence from the rest of the band is secondary, if it exists at all...like "Kilroy" and Journey's "Raised on Radio", or even BNW. IMO, even Edge suffers from Dennis controling the sound, without allowing JY to influence the music.
All of this to say - these guys apart will never be what they were together.
I would be completely happy if Tommy went back to creating DY albums, or solo albums like 7DZ. He reached an apex that he could have NEVER achieved with the limitations Dennis put on him in Styx. What did Dennis do after Edge? "10 On Broadway"? Hunchback? He is still hung up on making a "success" out of Hunchback. That is all he can come up with on his own? That REALLY shows how much he NEEDED the influence of JY and Tommy to create great rock music.