Cannot get APM to replace my Citrix Web Interface servers (5.4)

There could be a couple issues that affect you. I would suggest you use the latest iApp and deployment guide published here:

https://devcentral.f5.com/wiki/iapp.Citrix-VDI-v1-1-0.ashx

Couple of things to pay attention to - make sure you are using the right ports for XML brokers - some environments have them on port 8080, some on 80 - check the configuration that is being created make sure the objects use the right ports.

Check the XML broker pool and the monitor - if the monitor fails, then you certainly would not be able to reach the XML brokers(even if they are up). You can choose to use a simple monitor such as gateway_icmp or tcp to make sure that connectivity works properly, and then choose to troubleshoot the XML broker app-specific monitor later.