Mal, interesting post about DDOS attacks.  Let me comment.

The Delegates in our system, once voted into the 101 Club, remain there even if they fail to forge blocks sent to them.  There is not a system presently to demote a non-performing delegate to standby status.  Vultr shut off a dozen of our delegates yesterday due to a billing change (they dont bill PayPal accounts anymore).  We still had a viable network with only 90 delegates running.  I was unable to access my delegate on Vutr.  I simply opened the node on my laptop, and forged for 3 hours at home until Eric could straighten it out.  His delegates were offline for that period.

In every 101 block cycle, there are one or more blocks that dont get forged by the randomly chosen delegate.  The unforged block is sent to another delegate, and another until it is forged.  An attacker would have to DDOS  all 101 delegates at the same time to stop the network.  

The delegates are presently on cloud servers because they performed poorly on laptop and home PCs.  It is possible to run the network from home computers, its just slower and only has a 75% forging rate (for my computer anyway).