Well, I'm of the opinion that it's not the power/level of the caster that should affect the save DC, it's the spell slot level the spell was cast at.
If you're a 20th level caster and you cast Sleep using a 1st level slot... you're basically saying "I'm not putting any time, thought, or energy into this spell." Thus, the DC should be the same as a 1st level caster casting it (IE simpler to resist).
I feel this way on both sides... on scaling spell damage and scaling spell DCs. If you want more damage dice for your Fireball... you should have to use a higher spell slot. If you want a higher DC for your saving throws... you should have to use a higher spell slot.
And what does a high-level wizard do with all of his 1st level spell slots that he won't be using for attacks and defenses? He should now be using them for all of his utility spells that he used to cast in ritual form. So he no longer needs to spend 10 minutes to Comprehend Languages or Detect Magic like he used to as a youngster (in order to save his spell slots)... he can now cast it with a single action since he's not going to use the slot in combat for anything else.
That's my opinion at any rate.
If you're a 20th level caster and you cast Sleep using a 1st level slot... you're basically saying "I'm not putting any time, thought, or energy into this spell." Thus, the DC should be the same as a 1st level caster casting it (IE simpler to resist).
I feel this way on both sides... on scaling spell damage and scaling spell DCs. If you want more damage dice for your Fireball... you should have to use a higher spell slot. If you want a higher DC for your saving throws... you should have to use a higher spell slot.
And what does a high-level wizard do with all of his 1st level spell slots that he won't be using for attacks and defenses? He should now be using them for all of his utility spells that he used to cast in ritual form. So he no longer needs to spend 10 minutes to Comprehend Languages or Detect Magic like he used to as a youngster (in order to save his spell slots)... he can now cast it with a single action since he's not going to use the slot in combat for anything else.
That's my opinion at any rate.