I’ve set it up exactly per the examples given in this thread, which seems to be the general consensus on how to configure this. See scenario 2 of the ROAS configuration for the Router config download.
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
Not sure exactly what you are referring to as using the bridge as a “backend interface”. If I assign the DHCP server to the VLAN interface in this configuration, it will remain INVALID. If I assign an IP address to the Bridge interface (in the same subnet as one of the member VLANs), the DHCP server will become VALID but will not issue IP addresses, and I lose connectivity to the VLAN IP Gateway itself and can only reach the Bridge IP.
Conversely, if I remove the VLAN as a bridge member, the DHCP server will become VALID but then I lose Layer3 communication as well.
Thoughts? I can post config as well if that helps.