My guess is:
EA surface = Levels 1-5
Underdark/Grymforge/Shadow Cursed Land = Levels 5-6
Moonrise Towers = Levels 6-7
End of Act 1
Act 2 = Levels 7-9
Act 3 = Levels 10-12 tops, but probably more like Level 10 and maybe 11 by the time the game ends.
Remember, the higher the level, the more XP that's needed to level up, and if Larian does a cap on each act, you'll be lucky to get to 10.
