Ah. I misunderstood how you meant to use the rug--I thought you meant to use it as a blindfold, but you're actually using it as a source of dust. In that case, we're in the "dirt in eyes to blind the guy scenario". Rule of Yes would let you get a free round of blinding; on any other attempt I'd make that a DC 8 Con save to avoid one round of blindness. Generally rubbing dirt in someone's eyes is going to be better than throwing a bunch of dust in their face.
I don't have a Rule of Yes, and tend to arrive at a ruling to stick with. After all, there won't always be a rug to throw, or a building to leap off of. Even if there is a building or tree, the PC is sacrificing HP whenever they pull the trick, so I don't have much of an issue with them doing it repeatedly.
Also, from my point of view, the option the enemy has is to close his eyes or get dust in them, either of which leads to temporary blindness. The reason I would rule it as an improvised attack instead of a Con save is to emulate whether the enemy swipes the rug away quickly enough, as you don't really 'shrug off' blindness from dust in your eyes. Of course, these are all just me explaining my personal rulings, not me trying to sway your point of view.