You will need to use a filter when connecting the rj11 cable. Your existing Asus router is fine don't need to use hub.
If you can get Internet when using the test socket then you really don't need an engineer visit and it may cost you £129.99
if you have used the test socket and still no broadband but have a dialtone then suggests problem outside your home and need get engineer visit by phoning customer services
Faults 0330 123 4567
The filter is clearly quite complex given its size. Presumably there is something within it that responds to ping (or whatever the BT diagnostics use). Is there any other possible reason it's within the household?
There is nothing complex about a DSL filter, it is simply a passive filter to stop the broadband signal interfering with the phone signal.