A very common misconception about heroic strike that some warriors make is that heroic strike does a lot of damage. They say this because they see the numbers on their screen and in their combat log that says heroic strike did a lot of damage. While this is ok that they see this, the important thing to note is what you don’t see. And what you don’t see is a main hand auto attack. Most of heroic strikes damage which you see on your screen and in your combat log is actually damage that would have happened anyway.
if you did not que up a heroic strike because you would have had a normal auto attack from your main hand, so you would have done the same amount of damage, just 495 damage less.
please note that using heroic strike will prevent your mainhand swing from being a glancing blow, as well as making it affected by Impale. This means that over a longer time scale the DPS increase of using heroic strike will be more than just because of the addition of 495 damage. However this still does not make heroic strike an amazing DPS ability, you should be using Heroic strike as a rage dump and not an ability that can boost your DPS by a large amount.