Hi Andreas,
regarding a "linear workflow" to my knowledge a few things need to be considered:
World Texture Node:
By Setting the Power above 1 you are altering the HDRI. The Color Correction Node is clamping the HDRI
and thereby also altering the HDRI (You will see a drastic difference with or without Color Correction Node even with neutral Settings).
Intensity is better controled by the Power Settings in the Octane Environment.
The Gamma Value in the Camera Settings for Linear should be set to 1 (when Octane Camera Imager is enabled).
The Blender Color Management for Linear Workflow is sRGB for Display Device and RAW for View.
Gamma of 1 is Linear, 2.2 will give more or less what a monitor can display.
If you're happy with your Filmic result go for it.
By the way there's an interesting Tutorial on Color Management by Andrew Price:
https://www.youtube.com/watch?v=m9AT7H4GGrA