I thought the reasoning behind a Coppering attack is that people are unlikely to run out of Coppers in the supply even if the attack is successful over and over. This card happens to be fairly weak since it helps mild engine-players with its light trashing. Its basic ability is woodcutter, which isn't too strong by itself. Good defenses include mandarin, fortress, courtyard, scout?, cartographer, navigator, gardens, silk road, duke, draw-up-to, apothecary, estate-trashers, watchtower, trader. Strong against Scheme, alchemist (strong with as well), trading post, altar?, cellar?, pearl diver?, pawn? (those cheap cards might end up trashed). It seems okay.