New gear perks...
I like the look of Sentry's Call and Tactician's Authority. Although I think most will go for Striker's Battlegear.
Path of the Nomad is geared to the DZ (obviously) and I think you will only be able to collect items from the set there (not sure if they get dropped with Incursions).
Also, the bonus' also only apply once you have the full set of gear - so you have to build the set piece by piece.
Has to be said though, a group who has these all equipped will be pretty much invincible in the DZ - unless another group is equally kitted out. Might make the Supply Drops a bit tough...
EDIT - it appears those numbers next to the set bonus refer to how many items from the set you have equipped.