But is this not the same as trample?
You can not defend yourself against a trampling model, except diving for cover...
Unles you have other models on wait around which may charge the trampling model (from the side), same as with the swoop attack.
This is why I asked whether you may dive for cover as a reaction to a swoop attack.
To my embarassement, I just reread the rule, it says that you may dive for cover, doh!

So imo it is the same thing as with trample, you may only avoid the attack or you have to have other models accompanying your RK...
Do you have to face the model you swoop attack like the trample attack or can you turn and attack like on a charge?
Otherwise a model with 3 AC could swoop attack with all three actions, this is could be too much...