Is there an eyepiece or some sort of attachement that you can use attach to the rear view screen so that one can autofocus with zooms
No. You can get clip/strap/bolt on hoods like Hoodman, LCDVF, Zacutu etc that make manual focusing on the rear screen easier, but it won't make AF any better.
It is TERRIBLE for autofocus in video mode, in fact, I would be surprised if it could be considered autofocus,
Yes, AF in vidoe/live view IS terrible. Primarily because it uses contrast detect AF which is slow and not very good. AF is pretty much useless on video generally and is usually the first thing to get switched off by anyone that knows what they're doing. You won't find AF on any professional broadcast camera*.
There are some AF broadcast lenses made by Canon that work OK, but are extremely expensive and rare.