A lot of my friends are into wargaming so I tend to get asked questions about how I would do things. In this instance somebody had engraved a section of cobbles like this for use as a road, it took 25 minutes and he was keen to do it faster (and therefore cheaper). I suggested it would be better as a low power cut with the laser out of focus, this would give you wide lines that would look like an engrave. The equivalent cut took 7.5 minutes, over 3 times faster.
Defocusing the laser is a straight forward process, I simply put varying thicknesses of material under the height tool and set the laser up as usual. In this instance I achieved a suitable line thickness when the laser was 6mm out of focus.
I built the cobbles into a Z shape which can tessellate easily but also makes it harder to spot where the overlap pattern is, especially if you mirror and rotate the pattern as you go along. If you'd like to use this cobble pattern in your own designs, please feel free (svg here)