In the DV, power often comes with a drawback that prevents its overuse.
We've seen one artifact -- the Blackstaff -- with the power to eliminate the main drawback of black magic (the taint).
What if Rashid's Eye does something similar, but with the Sight? Maybe it acts as a filter -- the Eye uses the Sight and then passes a weaker version of the image on to Rashid. So he doesn't get an unforgettable memory and isn't overwhelmed.
This would let him, a mortal wizard, use the Sight nearly continuously -- like on a stream of fae soldiers marching back through the Outer Gates -- without losing his sanity, making it an excellent tool for exactly the job he does.
If this is right, then Rashid has more experience using the Sight than any sane wizard, by far. He should be really good at extracting information from the usually rather abstract information the Sight provides. (At least as we've seen it through Harry's third eye.)
This could explain a lot of his apparent Foresight, and what he did when his false eye looked Harry up and down at the docks on Demonreach.
Thoughts?