To those of you that are still lagging, do you mean FPS (frames per second) lag or net lag? If it's FPS, make sure your game is running in Direct3D mode in Options > Video > Rendering Subsystem. If it's on OpenGL like mine reverted back to in the patch update then it will FPS lag like crazy. If it's net lag that's not due to FH.
If you still can't get your patch to work even after using the installer then try this. Install it into your documents when you are asked where to install. Then go to your documents and copy everything within the patch folder. Go to your Feral Heart folder, paste, and click yes to overwrite on everything. This absolutely ensures that you are patched and, considering I'm in the game now with no issues, I've confirmed this works.
If you still have a problem, then it may be some sort of mod or secondary file that's possibly causing it. I don't know, that is mere speculation. I would recommend backing up your current FH folder to save any mods and trying a clean install.
It also seems the patch is still being worked on and updated? So while it may work for one hour it may not work for the next. It's hard to say.