Difficulty Numbers: Scaling, or Static?

[VHawkwinter]

It goes beyond DCs and TNs, of course. One of the frustrating ones for me is level based encounter charts (not Dungeon Level based ones, but PC level based ones). What lives in that forest should be true no matter who walks into it.

This is true; but you could decide that different parts of the forest have different CRs of apex predator who live within them without it being too crazy. Admittedly, if you're clueless and don't see the signs, you could stumble into the territory of a CR15 lich-spider or something; but someone with suitable knowledge(nature) should pick up hints before that happens.