I have a training Gerrit box running:
- change id required
- strategy = merge as required
- commit-msg hook installed and working
Regular commits work just fine, but after a merge commit made by Gerrit, pushes fail as the merge commit has no change ID
Asking around I've heard most people say they have strategy = rebase as necessary.
A similar question (Why does Gerrit not include the change-id into merge commits?) has a work around for the same issue using another hook.
My conclusion then is that merge as necessary and change-id required are incompatible but I can't find any confirmation of this