Northamptonshire had a bit of a fluky season last year in my opinion as everyone just seemed to perform so well (even those that hadn't done so before) but seem to be tailing off again. They've also been attacked by a lot of injurys and problems with overseas players.
In D2 you have Worcestershire, Hampshire, Surrey and Essex, all of which are teams I feel could be competitive in D1, the majority of which due to their batting lineup but there's still good bowlers chucked in there as well.