Just some observations:

1) Beasts/Monsters are NOT scaled. For example: The zombie you meet at level 16 is the same zombie you met at level 6. At 16 he's a pushover, at 6 he was tough.

2) Human melee enemies ARE scaled. e.g.: A Barbarian, at lvl 3, can be killed with 3 or 4 hits with an elven weapon. A Barbarian, at lvl 20, can need over a dozen hits with a daedric weapon.

3) Human spell casters are also scaled.

I have recently been experimenting with some super strong characters who are immune to Magic, Fire, Frost, and Shock.
Human spell casters haven't been able to touch me....until....as soon as I hit level 18 they start zapping me with spells for 50+ HP at a time. A few of these spells are ranged but most are touch. Spell Reflection and/or Shalidors Mirror will stop some of these spells but not all. 100 Willpower seems to have very little effect, if any. Spell Absorption doesn't seem to help either ( I have, though, been using characters with zero magicka, so I'm not sure I could/should absorb spells anyway).
With 500 - 900+ HP this is not too dangerous, but it is bothersome, and I'm curious as to what they're hitting me with.