What do you think will happen when BTC is at $10,000 per BTC to the alt coins? Will they still move at the same ratios? I am getting the feeling they might not due to perceived value but then again when you can buy an Alt coin with a strong network for a fraction of that, then perhaps they do move together. For comparisons sake XMR at .005 would equate to $50. Dark at .017 = $170.
On the last spike, when China was manic on BTC, it went manic on LTC even bigger, but slightly later. On the chart we see that during its heyday LTC\USD would lag BTC\USD at the start of a run-up, then slingshot beyond it at the peak. I think LTC's heyday is truly over, and don't expect it to exhibit the same behaviour on the next BTC spike, but DRK and XMR both may be subjected to this elastic-attachment mechanic.