firewall can ping them by host name, like host – or host.domain.tld ? You sure you not just broadcasting for the netbios name?
What is pfsense using for dns? You state your using your DC for dns and dhcp, so where does pfsense point? To itself using forwarder or resolver?
If pfsense is using itself which it should be, then you would need an override in the forwarder or resolver depending on which one your using to be able to resolve a fqdn from your AD.
As you can see in the attachment, pfsense can resolve local names just fine. If you point it to proper place to resolve them via dns. You can see my harmonyhub phoning home here.
Maybe your AD doesn't have the reverse zone setup correctly, or the entries are not being created either by the client or the dhcp server. Can you query your DC directly for the PTR record?
resolvelocalnames.png
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