latency/jitter measured via ping is about ~300ms during download pressure of 3 http transfers. The latency doesn't appear on synthetic bufferbloat benchmarks, though. (dslreports ; 20ms ("A")

question: trying to figure out why I'm seeing this particular behavior, and determine if it'd a real issue or just an anomalie with ICMP traffic

I've not seen ping do this with other modems. 

Perhaps I need to try some other traffic generation/ capture  tools?