What you describe is a user and resolver configuration problem. There are 100's of TLDs and there's always a chance they will conflict with subdomains, either now or in the future as new TLDs are created. I've been using both "int" and "dev" as subdomains since at least 2000 and never had an issue.
> What you describe is a user and resolver configuration problem.
That won't prevent me from getting a ticket saying "the network is down".
Okay, I guess the only solution is to always use FQDNs.