I think the DCs are off on skill challenges, as has been discussed elsewhere, but I think the main problem is actually early on. Later, you are expected to have any number of different bonuses going on from items, skill focus, higher stats, utility powers, etc.
I'm actually starting to wonder if part of the idea was that these things would actually be fairly hard to do and that challenges would be pretty tough to beat on average at low levels, unless you were true specialists. That might make sense, since it gives a real sense of progression and the party as a whole getting better at things. Of course the math is still off because when things are hard, higher complexity challenges are easier, but the DCs might be reasonable from this point of view.
I'm actually starting to wonder if part of the idea was that these things would actually be fairly hard to do and that challenges would be pretty tough to beat on average at low levels, unless you were true specialists. That might make sense, since it gives a real sense of progression and the party as a whole getting better at things. Of course the math is still off because when things are hard, higher complexity challenges are easier, but the DCs might be reasonable from this point of view.