I agree and IMO it's basically impossible to fully defend a dynamic site against a well-engineered L7 DDoS, short of operating at top-10-website scale and simpl

I agree and IMO it's basically impossible to fully defend a dynamic site against a well-engineered L7 DDoS, short of operating at top-10-website scale and simply have more resources than the attacker(s). That does create a sort of "survival of the largest" effect which is a concern for smaller startups which anger or frighten a much larger competitor.