That is the result for square pattern, channels made with 1.5 mm mill bit, no xy table, just hands...
Now, for circular pattern (I don't have the pic yet, I managed to do 1/3 of one half of the block today) it is much worse cos' you cannot go with straight moves and do lot's of holes, you can do only three holes at max in one straight cut. Other problem with doing this with mill bit of small dia is that you must do 3 or better 4 passes for every connection between two holes to remove all the remaining copper, mill bits I have have cutting flutes approx 1.5 mm high, so you first remove 1.5 mm height of copper connection, than lower the drill/mill and do another pass removing another 1.5 mm and in third pass you can remove all copper. That's just between TWO holes. Now imagine how many of them are here...
Yeah, you can do some holes in line like in square pattern, but connecting circular ones would be killer, even with dremel...