For trail riding with a little off trail now and then I'd look at the Tuner skis from Yamaha especially if you want to get rid of darting. I haven't used mine yet, but from everything I have heard and read they really do improve the Nytro's handling by a large measure.
Edit: After reading that you do go off trail a lot the Tuners probably aren't the ski for you. They are a little wider then the old stock skis, but probably not for a person that spends a lot of time off trail or boon docking.