Altostratus
AltostratusI managed as following to get everything working here:
First of all, once I started to use a self-ip address as listener and used this address as server address, the GTM has started to recognize itself and the others devices and since then the synchronization group, discovery e everything started to work as the related documentation suggests.
As I was using IP address in WIP pools without direct relationship with local virtual servers, I just created a fake monitor to make all objects up without really checking them.
Doing it, the DNS queries started to be really balanced in a round-robin fashion instead of returning always both addresses and, finally, stopped to return the address from a disabled data center.
I'm only worrying about having to leave the iQuery port open for a public accessible DNS address in the port lockdown settings for all self-ips used as listener. It's still sounding weird for me.