Adam Clarke on Job 30:13

They mar my path - They destroy the way-marks, so that there is no safety in travelling through the deserts, the guide-posts and way-marks being gone. These may be an allusion here to a besieged city: the besiegers strive by every means and way to distress the besieged; stopping up the fountains, breaking up the road, raising up towers to project arrows and stones into the city, called here raising up against it the ways of destruction, Job 30:12; preventing all succor and support.

They have no helper - "There is not an adviser among them." - Mr. Good. There is none to give them better instruction.