Algar looking Glass:
I found the response from the GC engineer. It won't mean much cut&pasted verbatim and out of context, so I'll just summarize.
Basically, I was seeing vastly different response times to given hosts in the same subnet on CTBC's network. My source ip was the same. Traceroute revealed to me the packets taking different paths, after hitting a particular GLBX router.
The GC engineer said CTBC is a customer that hangs off of this particular router, and that traffic was hitting an interface and hair-pinning back out to the customer's segment. He pointed to possible congestion on CTBCs switching fabric as the cause for the varied response times (conceivable) and different routes (um...ok maybe some kind of load-balancing at play).
I managed to call CTBC (Algar) and confirmed they were experiencing congestion issues and they had a scheduled circuit capacity upgrade with GLBX in a few weeks.
As a network admin, i find it sometimes sadly humorous how we can poke and prod at a problem, go through various carrier support channels and scratch our heads for hours/days when all it would normally take is a RO userid on a couple routers in the path to figure things out. that's not too much to ask, right? 
-matt