Alter Self, Polymorph Self, Polymorph Other, Shape Change
At their heart these are buff spells, and they are very, very overpowered compared to other buffs of the level. There is the "threat" of thse providing some inherent limitations to the character, but they really have no tactical bearing. Either these are all no-brainer spells for their level and all other buffs falter, or these need to be pulled in line. I pulled them in line.
Scrying, Greater Scrying, Greater Prying Eyes, Discern Location
Augury, Commune, Commune with Nature, Stone Tell, Find the Path, True Seeing
Why should these be so much more powerful than Gather Information or Diplomacy? I'm not a big fan of "absolutes" in the game. These deter from roleplaying, and end up being used as shortcuts, even encouraging the players to stall and cajole the casters into using them to "fast-forward" the plot. A slight change to make these skill-based challenges both align this better with other characters abilities and don't make these an "absolute" success for the players when casting.
Daze, Daze Monster, Fear, Calm, Charm Person, Command, Command Undead, Suggestion, Charm Monster, Greater Command, Magic Jar, Mass Suggestion, Symbol of Persuasion, Mass Charm Monster, Sleep, Deep Slumber, Symbol of Sleep, Sound Burst, Scintillating Pattern, Power Word, Stun, Symbol of Stunning, Feeblemind, Tasha's Unconrollable Hideous Laughter,
Otto's Irresistable Dance, Otiluke's Resilient Sphere, Forcecage, Mind Fog, Maze, Evard's Black Tentacles, Holy Word, Blasphemy, Word of Chaos, Control Undead, Imprisonment, Dominate Monster, Mass Hold Monster
By far the most powerful economy in the tactical game is that of actions. Any spells that limit, negate, or prevent actions are extremely powerful, particularly at higher levels, when the threat of losing all actions in a single blow is significantly diminished from any other source. I like handling these as a high-risk, high-reward debuff. These are all direct debuffs, comparable in effect to their level, but many are high-risk, high-reward actions that if successful result (like disintegrate) result in a powerful de-buff that affects an opponent (or group of opponents) to challenge both mental awareness (Surprise) and Mental Perserverance (Will to Act).
Phantasmal Killer, Slay Living, Circle of Death, Destruction, Power Word, Kill
Finger of Death, Wail of the Banshee. Implosion, Weird, Trap the Soul, Implosion, Flesh to Stone, Earthquake
Again, as above, anything that can instantly eliminate a threat is radically more powerful than most spells of the level. These are the classic high-risk, high-reward play, and I think the 3.5 version of disintegrate handled this line the best, and provided us with a superior model for balance.
Anti-magic shell
Really? Either the single most powerful spell in the game, or totally broken.
Enervation
So, I would challenge you to think why you find this to be your favorite spell? You know how fun it is for yoru PC's to lose Con or levels. Yeah, that's not cool. These are all debuffs at their heart, and should be pulled in line with other debuffs of their level.