The only worthwhile "arcs" in that show were on Evangeline Lilly and that Korean lady.
As to episodes, I agree the first 60 or so were good, but only because they built suspense.
The latter 60 were painfully bad as they exposed there would be no payoff resolution.
If we want to blame it on the network and give the writers a pass, that's fine. But somebody should have gone to jail.