I use glyphed Heroic throws to put sunders up.
Heroic Throw is a 1min CD, Sunder Armor is a 30 second debuff. I don't see how there is any point to this.
I start every fight at range, and use heroic throw before I intercept (so it doesn't reset swing timer, since I'm not even in range to swing yet).
If you do this, then you won't land any autoswings for 2-3 seconds at the start of the fight while you wait for your swing timer to reset. You lose 3 seconds of autoswing rage generation and the white damage itself.
You're right about it resetting the swing timer, but you could easily get a swing timer addon...
This won't work unless your weapons are the exact same speed and are kept synchronized. Different speed weapons will get farther and farther apart, but when you Heroic Throw it will reset both your mainhand and offhand swing timer.
Also note that, even if you have two weapons of the same speed, by default the swing timers will be staggered when you start attacking. You can either Heroic Throw to synchronize them, or if the target is attackable before you pull, if you start autoattacking from range (so that your character draws his weapons and will begin autoswinging as soon as the target is in range), then your attacks will be synchronized.
Heroic Throw should be a DPS loss if you are dual wielding with different speed weapons.