Paul,
The delay is about a second or so, as you said. But note, no other GPU render engine I use has this delay in the viewport (including Iray and the standalone Octane); they all update instantaneously on my dual 1080 Ti's. It is only the Octane plugin that has this delay, which seems to suggest that there is a communication bottlenck between DS and Octane.
If you want, I can do a screen capture for you and post the recording comparing the two. It is enough of a delay to discourage one from using Octane, as live feedback is important to workflow (and Octane has long been known to deliver live feedback in the viewport... so I don't know how this can be described as normal). For the amount of money one pays to obtain this plugin, I don't think this should be happening.
Thanks again for all your hard work,
-P