ClickToPlugin works like a charm on Safari (and it removes all video ads as a side effect).

I'm not in any way affiliated with the developer of ClickToPlugin, I've just been using it to the effect described by OP for some time and it's the only thing that's been keeping me on Safari for a while.

check back here in like 10 minutes or so

edit: just waiting a few more mins on the CSR stuff

There's Youtube5 extension for safari.