I think we will be more of a support, but im just guessing at this point. I say this for the reason that phantasms just die way to easy to any aoe, which will probably be a huge factor in raids. However, there may be some fights where a band of duelists may be safe to fire most of the fight and provide great sustain.
My guess? Support most of the time, with some fights being dps, but only when you can reliably have your phantasms active.