It would be interesting to know the percentage of wood boards and the percentage of dram boards that get returned/repaired under warranty. Having said that, I bet most returned boards are damaged by couriers during shipping to the dealer.
Apart from catapult damage (which would hurt the nose of any board) and the odd chip on the rails, I've rarely seen damage to the wood dram boards. It's true that modern construction is less robust than boards of old but if the market demands a higher performing and lighter board then we must expect some compromises. Imagine the weight of an injection moulded formula board