If there's problems that have been worsened due to a official patch, it would be nice to know how to downgrade from a patch to another.

You cant.

That worked back when the first patch was released -- unfortunately Steam does not allow rolling back and no longer has the ffiles needed for other patches available - so there is no method to roll back to any version other than the latest since even deleting the game and reinstalling from the original DVD requires connecting to STEAM to activate the install at which time the latest patch will auto install before the game can be launched ! -- So in order to roll back you would need a working older version back up ( Win 7's roll back option might work if only wanting to go back one version - but the latest update was relaunched after a couple days to fix an additional bug thus most systems currently have 2 versions off the 1.9 patch and rolling back will only roll back to the first 1.9 version making it useless any way !!

So unless you have a back up copy of the files on your system or another system you have access to and you can get STEAM to actually launch in off line mode (works ffor some but not others and if STEAM connects online for ANY GAME it will auto update again as soon as it connects) so as was stated there is no way of rolling back and playing with the rolled back version.

You can use Windows' "previous version" of your Skyrim folder.