The Necro's Shades cannot do damage anymore when placed on (the edge of) walls/battlement, hills, ramps, bridges and many more. Also the slightest difference in elevation or loss of LoS due to rocks, trees, ... results in "Obstructed! Obstructed! Obstructed!" ... Sometimes staff marks get triggered but don't to damage/effect won't happen, too.
This seems unintended because i.e. Elementalists are still able to do damage with their skills.
EDIT: It's not walls only. The smallest difference in elevation results in "Obstructed!"
EDIT2: Or objects in LoS ...