Yes, this is one of those cases where I think the intent of the ability is more important than the exact text. This one is hard to describe for designers, especially with how complicated the rules interactions have become.
If I was to reword the feat the way I believe it is MEANT to be played, it would be this:
As a full round action, you may make one immediate attack against each opponent within your threatened area. You forgo all additional attacks that you may get this round. You may not make any movement between attacks, however you may make a 5-ft step before or after all your attacks.
The idea being, you stand in one spot, swing your sword around and hit everyone it can hit. Thus, I would allow a character in a DD to use whirlwind attack, but they wouldn't get to move between attacks. I'd allow this because despite the exact text, I think Whirlwind Attack was not meant to be a full attack action, just a full round action that gave you attacks.