Summary: This draft is almost ready for publication as a standard track RFC.

Major issues:

Minor issues:

“the specification of a DHCPv6 option that could be used to discover
   unicast PREFIX64s in environments where multicast is not enabled.
   Such side effect conflicts with the recommendation documented in
   Section 6 of [RFC7051].”

It is unclear how the Section 6 of RFC7051 relevant with the content above. It would be necessary to quote particular content of RFC7051 and give necessary analysis.

Nits:

“the Pv4 multicast address is inserted in the last 32 bits of the IPv4-embedded IPv6
   multicast address.”

Pv4//IPv4