Route Domains were a compromise with our security team, they really don't like the fact that we only have 1 F5 and when we put in our routes originally to separate the traffic we ran into some asymmetrical routing issues. The idea behind implementing route domains was to get us past the routing issue and allow us to route specific traffic over certain routes to make sure that DMZ traffic never touches Prod traffic and etc.
I know the whole thing sounds a little crazy and the way we originally had it setup worked just fine, but security didn't like it.