My wife and I play multiplayer pretty often, connecting via a decently powered Windows 10 gaming desktop and a Mac laptop that has to run on low graphics settings. Prior to the Palace of Ice update, we would only experience de-sync rarely, and usually only after we had left the game unattended for some time. Now we are getting de-synced almost every combat, often during the first or second round. Every time, restarting the game on both systems, and then reconnecting will allow us to get through that combat encounter. However, then we de-sync again in fairly soon after (but always during combat.)
We haven't troubleshot it much, but we did try lowering graphics settings on both systems, and it doesn't seem to change anything.