I was always looking forward to bigger and more destructive spells to deal with the trash fights faster but they always disappointed (as many people warned). That's because the monsters always seem to have about 10 times more HP than is your reliable (green range) destructive spell dmg output. By the time you get WMDs like Nuclear Blast or Earthquake, enemies start in the 300 HP range
and have 80+ elemental damage resistance
and many of them cast Elemental Shield. This renders those spells effectively useless. For the same reason the instant death-type spells like Asphyxiation, Death Wish or Quicksand are doubly useless (moreover the 7th level spells like Death Wish come very late in the game, if you don't powerplay, I got mine on the Ascension Peak

)
And as for the disabling magic, most of it is also pointless, when Paralyze or Web is rarely successful and Blind is more annoying than anything since blinded monsters run away. Best magic school by far seems to be Psionics (in W7 it is the worst), at least this one becomes useless only at the very end.
On the other hand some protective spells - Magic Screen, Soul Shield, Elemental Shield and Missile Shield - seems a tad bit overpowered. Combined with high resistances my chars accumulated through leveling monsters could hardly touch me. The last fight was a joke and I was only about level 22. Also, as a side note, after dozens of hours of playing I still have no idea what
exactly spells like Bless, Armorplate and Enchanted Sword actually do.
(Also, fuck Gadgeteer next time. Most gadgets come late, there are much fewer of them than music instruments and many are underpowered. The Omnigun can be decent but blinds very often, which is annoying, and the ultimate - and truly awesome - addon comes at lvl 26 which means 25 million XP. Fuck that, next time I take Bard).