My blue (SA) XT660Z has done quite a lot of dirt and dust riding with a DNA filter without getting any dust or dirt inside the filter. Suppose if it's oiled properly it should serve for all conditions.
My Australian ZT660Z 2015 model came out with a standard OEM paper filter and I've also replaced that with a DNA filter and lid (stage 1.5 at his stage).
The main reason for changing is the better breathing and nippier performance.

__________________
2014 XT660Z - Barrett pipe, DNA stage1.5, Barkbuster hand guards and handlebars, Pivot pegs, Teknik suspension, Guard-it engine protector combo, B&B rear rack, Trax topbox.