Something else to consider. Everyone (well not everyone) is complaining about the CRs being too low...blah blah blah. Or how Graz'zt can be beaten by a 20th-level or 24th-level or whatever party.
Now, what are the chances your party is ever gonna catch them alone? Sure, one-on-one (party vs. demon prince) might be a slaughter in the party's favor (and depending on the power level, it should be. There is nothing that can't be killed at some point, if it is statted. Make them 90 HD? Big deal. A 120th-level party (which can be done with the ELH) will kill them. "If you stat it, they will kill it." If you want them unkillable, don't stat them.
But, all smart demon princes and devils will NEVER be caught alone. Caught alone? Gate in/summon demons or devils. Teleport away. Send for help. Whatever.
The biggest thing about "Oh we whipped Orcus' ass in no time flat." Good for you. Now, if your DM played him anything like I've seen and read a lot of other DMs playing demon princes, dragons, etc. then he didn't play him to his fullest potential. He played him as just another monster. And that fault lies with the DM, not the designers.
As for the power levels in the BoVD. I see no real issues (to me anyway). I think they scale nicely with the other 3e stuff. They are not as powerful as gods (and they shouldn't be; they aren't gods).
But the bottom line is this. Had WotC made them divine and godly, half the people would've been happy, the other half would've pissed and moaned about rules contradictions between the BoVD, DDG, and DotF. Same thing for the way they did them. Didnt make them divine, so half the people are happy, and half are screaming that they should be divine.
Why not take what was given, use it as a framework, and adjust it as you see fit for your campaign? That is what all the books are for anyway, right? If you dont like something, do your own version or change the existing one until you do like it. And remember, it is a game afterall, so what's the big deal. Screaming about how they should've done that or should've done this, doesn't really matter now. The book is out. Its done. Time to move on.
