I totally get it. I just happen to work on the IT team that manages our companies mobile devices, so I’m not too fused about the privacy implications of putting some personal things on a work device. I know my personal data is kept separate, and I have backups of any data that is important.
Definitely agree they should be split up if possible. Octoprint and Home Assistant are both rather demanding on a Pi, particularly the Pi 3B.
I would however opt to run Pi-Hole on the Home Assistant device as there is a plugin built in for it, and Home Assistant is the kind of thing you would be more likely to leave on at all times.