So you simply want to route traffic based on a persons geographic location.
If only the "pool for HA" is missing, you can setup keepalived on both datacenters to handle the failover.
So you get:
- Your DNS servers will decide to which datacenter the traffic will go (put ns1 in EAST, ns2 in WEST and both AUTH).
- At the datacenters your keepalived server(s) will send the request to a up and running server within that datacenter.
Et voila .. and this solution will cost you a few simple barebone servers.