It's a 10 second recast.
I'll have to double-check the text of Perceptor's Command now - I remember it saying that it increases Threat (for the pet) by 784, not that it bumps the pet up actual hate positions too. Wouldn't be surprised though if there was some verbage in there that might sound like it was talking about positions on mob hate lists - plenty of unclear text in skills and abilities everywhere.
As I understand it though, it's a pet taunt for 784, nothing more. The % chance talked about in the description, rising in rank, is the chance of the taunt NOT being outright resisted - at rank 8 (100%), it isn't resisted - though it may not be enough spike hate to pull aggro back from an overzealous Necromancer. I've had plenty of times where I went a bit overboard, peeled aggro, and a single use of PC wasn't enough to get aggro back on my pet (though a stun, fear/root, etc, and a second PC would normally do the trick).