That sounds like a solution to a problem. Can you share the problem?
In general, you can make explicit rules for traffic leaving an interface, but traffic arriving at the interface is managed automatically by Astaro QoS.
Basically, there are two sites that are top priorities. So if possible, any user going to either of those 2 sites, those users will have the bandwidth allocated to them over any other site. Any suggestions?
Create a traffic selector '[two sites] -> Any -> Any' and use it with a Bandwidth pool on the Internal interface guaranteeing 90% (for example) of your WAN download bandwidth.
Since big uploads also can block HTTP requests, you might want to put another bandwidth pool on the External interface guaranteeing, for example, 100kb to 'Any -> Any -> [two sites]'.
If each site needs to be defined as a DNS group, then be aware that you cannot do a group of groups, and you'd need separate traffic definitions for each.
