prosfilaes
Adventurer
And I think you are missing my point: In order for magic to be "mysterious" (whatever that means - see below) it doesn't have to be mysterious to the players. That's simply a matter of roleplaying and presentation.
My statement was a reply to:
But I digress. The issue I see is that players with support roles use their OMG powers at the wrong time. Instead of seeing if the mundane methods work first they rely on the supernatural.. leading to a less mystifying experience of magic at the game table
I don't think it's possible for standard D&D (or GURPS) magic to be a mystifying experience at the game table. They're simply too cut and dried.
Magic being mysterious to people in the setting is completely setting-dependent.
To most people, but to wizards, no matter how you chrome it, it's got to come off a bit like stage magic. It may impress the plebes, it may even take quite a bit of practice and skill, but it's basically doing the same rote tricks over and over again. To a wizard's adventuring party, there's nothing mysterious about the dozenth fireball to go wizzing over their heads.
Anyway, I think you're actually using the wrong term in your argument. You seem to be concerned about predictability, not mysteriousness.
I'm concerned about whether magic feels like operating simple reliable machinery or putting your soul on the line wrestling with creatures from the beyond--or at least something situation-dependent and hard to handle and predict.
If you want unpredictability, all it takes is a (skill) check to determine if (and possibly to what degree) a spellcasting attempt is successful.
Not for a truly mysterious casting. A skill check makes it less reliable, but not really less predictable. Something like good old-school 2ed wild magic is a start, where things can happen that are truly unexpected when casting a spell.