Sorry for the hijacking.
Anyway my take on high level play is that you need to rely on your gut instinct a lot and on rules very little. But thats the advice you have gotten already
Oh well. Another broken 3.0 spell (and a bunch of real rules wise power gamers). I'll have to agree that your example pretty much sums up all that was wrong with 3.0 in one encounter. At least all those spells and items got nerfed.
And man Balors were wimpy in 3.0. Good thing he got it though. Before it annihilated the party with that firestorm/implosion
Its pretty hard to find the 3.0 succubus CR 9 reasonable as well: Basically one in ten encounters for a 9th level party would end in a TPK (or as Rystils example shows a little less than one in ten encounters).
Now a days a succubus can try to summon a Vrock, much better choise.