The Dragon Magazine had got the Savant class but it was a spellcaster, like the Archivist class from "Heroes of Horror".
A sage in a D&D squad is like to mix CSI and SWAT. They are different styles. A (no-magic) sage is too weak in the hard battlefield. And lots of players would rather to use magic tricks to find clues for an investigation.
I see a scholar/sage class as an adventuring learned man.
I could see it having:
- Expertise
- Bonus languages
- 4e's Int to AC
- Ways to add Int, Wis, or Cha to attack or damage rolls
- Charming people by just talking to them
- Surgery boosted by magic
- identifying weakness in enemies
- Buffs as "fantasy battle tactics"