A bit of a zombie thread, but for those with the same problem, it is the presets that set the volume to 100% and Line 6 hasn’t released a patch to allow you to mod the presets, and therefore the volume is always full blast:
Honestly, the fact that the Valve ii was one of the higher end models and Line 6 couldn’t be bothered to do a firmware patch to resolve this is just stupid. Great amp that is almost unusable with the presets and therefore forces you to make all of your own custom patches.
Copy the preset settings and make your own custom channel clones and change the volume on all of them to something manageable.