Hosts are also not on the plan, primarily because there already exist better caching mechanisms such as dnsmasq. Secondarily, the long-term plan over the next few years is to convert hosts lookups to using unbound or other similar projects to enable dnssec, which necessitates a caching application on the client machine anyway. So SSSD would become superfluous in that situation in any case.

Cheers for the info Stephen - nscd it is for now then (hadoop bug causing very high levels of negative lookups impacting my DNS infrastructure essentially)