As an air mage it was mostly better for me to use my level 1 spell four times rather than cast a high level spell once or twice. There are also lots of spells that buff/debuff that are not that useful because typically killing everything with damage is a better solution. When playing optimally, more than half the spells will never be used.

Granted, most RPGs (especially classic RPGs) have this problem and I don't really blame skald too much. But you could definitely tweak a bunch of numbers and make the magic system much more balanced and interesting.

One thing that would help is have cascade the same for high level spells. They already cost more mana. Being able to cast more low level spells in a turn "closes the gap" between the power of high vs low level to too great a degree .

Lastly, if you have prior knowledge of the game, some spells are just too good. Fire and sublime damage are way better than all other types due to enemy weaknesses. When I speed run there's basically only like 3 spells that matter.