Well it looks like dar may be getting hung up afterall. When I thought the previous backup was hungup on the dar process I ran a -t on the archive in another terminal. I eventually returned to the original terminal window and saw the output summary and at that point thought it finished.
This time around I've not done anything and it's been sitting here for more than 10minutes.
Code:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1152 root 39 19 15836 11m 2016 R 64.1 1.6 10:21.07 dar
It's late and I should sleep, I'll let it run overnight to see if it's going to finish on its own. The CPU utilization keeps fluctuating which seems to hint that it's not hung. But requiring more than now 12min of processing time just to create a single archive on a local hard disk seems excessive.