Seriously, why do you want it. It's not because it's theoretically the best, you should try and get one. Spirit will probably be good enough. or something like +2 cold spells/20FCR/+2Blizzard.
That's purely a matter of opinion. That rare orb will provide a higher damage potential for Blizzard, but that's it. On the other hand the Oculus gives more mods than just damage to make up for the slightly lower damage potential.
