From my point of view the tickets from Phabricator are more for developers. At the moment, we don't allow the client to create tickets in our Phabricator instance.
But, in the same time, it would be cool if the client can create tickets on another platform and tickets related to development get linked/recreated in our Phabricator instance.
I am more wandering how other companies which are using Phabircator manage the ticketing system between developers and the client.