I have a dhcp client with 2 interfaces. Both are set to DHCP. On the dhcp server side - running isc-dhcp - I can configure the search domains. The client goes to the dhcp server for interface0 and ...
(I wasn't entirely sure where to post this, but figured since it's only affecting my iOS devices specifically, I'd have a better chance of someone having come across something similiar in the Mac Ach) ...