All battery buffers ZPM and above don't work, don't input or output energy from any face, while battery buffers LuV and lower work just fine.

This does seem to be the case. Needs more testing to find out the cause.

CEFs and CEUs don't work sending a redstone signal with a comparator like a buffer does, if they would it would be a workaround, since that's the only reason I'm using a buffer in the first place.

This sounds like a problem with either GTCE or SoG. I don't think we can do anything about it unless they fix it. If it's fixed in a newer version, we can incorporate that eventually to resolve the issue, otherwise it's out of our control.