One of the orcs worst enemies are the outlanders who can just be chameleoned in hordes and attack, flee and then chameleon again. The orcs are wiley and naturally warey creatures from lives of violence and so could possibly have an ability to sense attacks from the shadows similar to the legacy but perhaps a diluted version. Alternatively they could, when engaged in fighting release a smell from a gland on their body to allow them to locate the camo/chameleon/hidden person until it wears off so that they could reengage or know if they are still lurking about.

Again, just an idea.

-----Abernyte