Multiple VMs one public IP, port forwarding on Azure Resource Manager

If you want a single public IP with say port 80 going to VM1 and port 443 going to VM2 this is what you do.

The trick is to use an availability set. So when you create the servers they must all be added to the same Availability Set, yes I know you aren't doing load balancing, just add them. Don't add a Public IP on the VMs.

Now create a Load Balancer with a Public IP.
  Now create an Inbound NAT rule, selecting the Availability Set will now prompt you for the target VM and NIC.

Each new Inbound NAT Rule can point to a different Network Interface within the Availability Set.