Nothing terrible as in outright heresy. Just IMO he’s too liberal, too light-weight, too close to the Charismatic Movement and like many converted Protestants, especially Protestant ministers, brings a blend of Protestant theology into the Church. I won’t post specific links at this time because I don’t feel like taking the time to find them, but would refer to the opinions of Robert Sungenis and others who have written on some of Hahn’s writings in The Remnant and other mags.
As for John Dominic Crossan, the guy is simply bad news for Christians of all denominations. Same for the Jesus Project.