When your spellcaster (especially mage) gets his/her turn you want to make it count. A good spell can turn the fight around completely, so you don't want to waste your turn casting a weak spell. Unfortunately that means that some spells are simply not worth casting in any part of the game. These are typically buf spells and defensive spells, but also a few offensive ones as well. The thing is that the fight is usually over by the time you might have reaped the benefits of investing in a defence or a buf.
I found 3 defensive spells that were powerful enough to invest in, and they were so powerful I would never want to be without them: Shield, counterspell and globe of invulnerability. In fact having all 3 makes it very hard for you to lose a fight. There are some cleric spells that may be considered defensive, although they can be used offensively which are also worth memorizing.
Magic missiles is a must. I think around 50% of the time my mages ended up casting magic missiles, mostly because they always hit the target, and bypass all resistances.
Point is there is a big number of spells that are quite useless in comparison, even if you use them creatively. Why then have these in the game at all? Or why not spice them up so they become useful?
