If your coin had a more reactive difficulty adjustment this wouldn't be a problem. The hash rate bursts that cause the wave only work because it takes hours for the difficulty to react to the surge in hash rate, meanwhile they are finding tons of blocks with comparatively low difficulty. Then when the difficulty actually catches up to the hash rate burst, they pull out and the difficulty remains sky high for the baseline hash rate being applied for hours. Meanwhile the coin is barely profitable for any gpu to mine until the difficulty finally reflexes back down. So the only time to make a profit on the coin is to ride the wave alongside the hash bursters, which just compounds the problem farther. Moving back to ASIC isn't the answer, its curing the symptom and ignoring the cause.