First off for this to work, you need to be Combat spec, with and have 1-2 points in Unfair Advantage. Next, you need Crippling Poison on your main weapon.
Now whenever you are mounted, and running through a group of mobs, every time you dodge an attack you have a chance to hit the mob with your main weapon (looks funny seeing your rogue jump and turn off the mount). When the main weapon hits, you again can proc a hit with the Crippling Poison, which in turn will slow the attacker. This is great for attackers which have a speed boost like some in Outlands or hunter pets.
Searched, but dunno if its a repost.