You know, David - I totally agree with you where the inclusion of cover songs in their live set is concerned; yawn - not all that interesting at all.
That said, it's not as if Glenn hasn't had cover songs on his solo albums or in his live sets either - "I Just Want to Celebrate" and "Nights in White Satin" come to mind right off the bat in that regard.
At the end of the day, though, what I really like about TDD vis-à-vis what they put out to work with Glenn really comes down to two words; flash and swagger.
Glenn is a white-hot singer, and he needs a band with a bit more vigor to stand up to what he throws down with, especially in a hard rock context, and I've always felt that he was at his best with a strong and truly virtuosic rock guitarist as his main foil, which is why I love seeing him work here with Doug Aldrich. For my tastes, this pairing sort of sits in that sweet pocket that past endeavors with Pat Thrall, Gary Moore and John Norum have displayed.
I'm not saying that "Radiance" is necessarily the best album that Glenn has ever done, but I do feel that, taken as a whole, it is the best Daisies album he's done so far, and I look forward to seeing this outfit grow further...
I should add that I have nothing against BCC. They are a great unit, no question about it, but for me Joe Bonamassa isn't quite the kind of guitar player I really like seeing Glenn with in a rock context. Bonamassa is without a doubt the most brilliant blues / blues-rock guitarist out there today, but as a hard rock player somehow he just doesn't punch all the buttons for me. In BCC he seems more "able" than "brilliant" to me...
In the end it all comes down to personal taste, of course, and in that respect nobody's personal tastes are ever wrong, which is what makes these debates so interesting!
As an aside, I'd add that another guitar player I have long wished that Glenn would work with is Jake E Lee. If ever Glenn wanted to go back to an energetic power trio a-la Trapeze, I'd love to see what that might sound like if he and Jake were to do something together along those lines...