yeah, but the fact that things are being worked on does suggest that the discussions we are having may unfold some influence on the shape the game takes.
frighteningly powerful is still my preference. with the spell power bar, one could introduce variable risks, depending on your skill, your ambition, and your present situation/condition. such risks could take similar form to the process of glyph research - damage due to failed attempts.
other ways to balance overly-powerful spells might include spell mishaps, e.g. an entirely different spell effect, or a spell effect unfolds on a different target ("sorry mate, didn't mean to turn you into a turkey..."), or equipment is damaged due to an uncontrolled discharge of magical energies...the devs' imagination and ingenuity is the limit.

also, the process of spell learning could be something run via other player characters. this could encourage the development of realistic rp-like mage guilds and hierarchies of teachers, practitioners, students, novices, etc who learn from each other - up to the point of secret traditions of guild-specific spells.
i think the entire magic field provides huge opportunities to introduce player-driven mystique and dynamic politics into this aspect of the game without devoting too much focus to how spells compare with weapons as a combat strategy. magic runs much deeper than this.