Since the pools can now be set up with the interface names does this also alleviate the requirement of separate subnets for each WAN interface?

Sorry, no, they still have to be in unique subnets.

How would DynDns work with dual wan?  I have an email server and several others that I need to port forward to using Dyndns.  Any example setups would be appreciated.

This will work for incoming mail, as long as you have a way of updating the dyndns service with the changed IP (I'm not sure how you would do that bit), but unless both your connections are with the same ISP, you may not be able to send mail whan failed over as it won't be coming from an acceptable subnet.