I agree with what's being said in this thread: 4e doesn't have a "sweet spot" as such, but the different tiers have different feels and impose different sorts of demands on players and GM.
Neverwinter is worth looking at for someone who wants to stick to the mechanics of Heroic Tier.
And Sage of Ages does start to break the maths of skill checks.
Neverwinter is worth looking at for someone who wants to stick to the mechanics of Heroic Tier.
And Sage of Ages does start to break the maths of skill checks.