So basically the title. Since the latest patch, monster HP bars and their name no longer show up above the monsters (except for bosses). And yes, the option of showing monster HP and name is enabled in system settings. and the animation of arrow rain when the arrows fall down out of the sky, doesn't show up anymore (the hit and cast animation still do weirdly).
I can use arrow rain and the animation still show up, I don't believe the Halloween patch would have made any changes to skills since the patch didn't even have skill files to download. I suggest you try re install the setup. The hp bar issue has always fixed itself after a few days for those that have had that problem.