I have ran across a customer using an old Linksys VPN router with DMZ and load balancing capability. The router is connected to a single DSL link. I am installing a Mikrotik to replace the Linksys but I am not sure how to reproduce the config. I have been thinking in the direction of using the first interface as a switch port and connecting the DSL Link to this. I guess I can create two virtual interfaces with the public IPs and route them. I tried applying the two statics to the same interface and this did not work. Any suggestions or advice?

You can have as many subnets and IPs assigned to a given interface as you want. Please provide an /ip address print detail, that way we can see what you are trying to do, and might be able to give some advice.

Each interface on the router can be it's own separate routed interface, so setting up a DMZ on the router is as simple as placing a different subnet on one interface and applying different NAT rules and firewall rules.

Thanks. I created a bridge containing the WAN link and assigned the two statics to the bridge. I performed a one-to-one NAT on one of the IPs for a specific server and I configured the remainder of traffic to NAT using the other static. The firewall rules hurt my head though. I'm weak in that area to begin with and I had to rethink how outside traffic would hit the bridge interface.

There's no need for any of that. You can apply two static IPs to a physical interface just fine. If it did not work for you then you had an error in the implementation somewhere.