Question about Righteous Defence

Hi All,
Have a somewhat "noobie" question about our taunt. I know the warrior taunt gives the warrior the same threat as the person he is taunting, and thusly makes sure the taunted target stays on him. (obviously if the warrior then fails to increase the threat he could lose the mob back to some over zealous DPS).
Does our Righteous Defence do the same thing? Give us the same threst as the previous target, so we can then build a threat lead? Or is it just a 3sec taunt, and once it wears off the mob will go back to the person on top of his aggro table? I only ask as it doesn't give a very clear discription of the spell on WoWwiki, and i thought you educated ladied and gents would b e the best source of information.

Many Thanks

Mandorallen - EU - Aszune