You mention that the revocation-check problem is old, which is certainly true, but I think you allude to the possibility that a domain-registry-based hierarchy will exacerbate that problem in the form of an increase in revocation checks. I'm not sure that would be the case; it should be about the same. What difference does it make if I owned a domain, got a cert from a CA, and stopped owning the domain -- vs -- got that cert from my registrar? If anything this helps the process, because my registrar knows when I stop owning the domain whereas a CA has no clue and relies on the cert's expiration date exclusively.