It depends on the value you are getting from this content check monitor. If it helps you to reliably determine the server state, you should discuss with the application team why the response takes so long. In the end it should be their interest as well that the BIG-IP can quickly check the state of the server and does not impose additional load on the server by querying dymanic URLs.
You could tune your health monitor too.
With "time curl http://backend/status.php?appID=02" you can measure the time the server needs to respond and adjust your monitor.
Or you check whether an adaptive monitor or an EAV external monitor might be of use for your case.