Bad Spell Buffs
I think one of the main problems with the Upper level Core Spells are spells that offer immunities rather than bonuses and a lack of Core spells meant to negate counter "game breakers".
First, let's talk about Freedom of Movement. A 4th level spell that prevents an Epic Dragon from grappling a halfling wizard. This is bunk. It should offer a nice bonus, like +caster level, to either the character's Escape Artist check or Grapple Check. This way grapple still means something.
Hero's Feast: Offer a competence bonus, 1/2 caster level, to saves versus poison, rather than offer immunity.
Find the Path: Rather than automatically detecting traps, solutions to puzzles, and acting as the magical GPS system, offer a competence bonus, caster level, to survival checks to determine direction, search checks to find traps, and knowledge dungeoneering to navigate towards the goal.
Death Ward: Rather than offer complete immunity to all negative energy and death effects, offer a sacred bonus, caster level, to saving throws made to negate/ignore energy drain, ability drain, and negative energy.
Right now each of those spells just turns off threats from grappling, poison, and getting lost/ detecting traps, and dealing with Undead, so DM's stop using them as they become futile. Using a bonus, means the DM can still use them and can make the grapplers bigger, the poison deadlier, the traps harder to find, and the undead meaner.
Teleport, Scry, Divination, Fly, Etheral Jaunt, Plane Shift, and Disjunction all have game breaking abilities, for a DM who can't answer the question, "If they've been hunting down the high level mage all this time, why didn't he just scry buff and teleport them 5 levels ago when he could have taken them easy?"
Each of these need some sort of basic counter that is readily available at a lower level, but not perfectly a guaranteed success. Something that allows the player to have plausible deniable on the internal consistancy of the magic level in the world.
In my campaign world, I couldn't comprehend a way to not hose the players with multiple Disjunctions that allowed the villains to seem intelligent. So I built in a mechanic where IC the Archmage guild delivers a message to every wizard as they hit 13th level, with a note of congratulations, and a warning, "Thou Shalt not Disjoin." With the implied message that if they did, they would be buffed, scryed and teleported.
Haste has slow. Why can't Fly have Land, a second level spell an evil Cleric could attach to his unhallowed ballroom, so his skeleton archers from the balcony above can pick off people entering the room?
If you could make it easier for DM's to keep the campaign world grounded and consistent with the "game breakers", the spells that change the way your players play, more campaigns would succeed into the later levels.
(I finally gave up. I'm ending my campaign after 1 more session. My players are 24th level.)