First off, welcome to the forums! Secondly, we here fully understand english as a second languange (you are not the only person for whom this is true).
Now, as to your comments, your example supposes that the attacker will only get 2 points above DEF when attacking in each of his attacks. That will not always be the case. And with exploding dice rolls, it is relatively simple to get 5 or even 10 points or more above the foe's DEF. And then don't forget the Boons, which can increase the amount of damage done by a good bit.
I guess that what I am saying is that if you do not include exploding dice rolls and Boons, then yes, it could easily take that long to defeat a foe. However, if you do include those, you could conceivably defeat that foe in 2 or 3 rounds (or even in a single round if your roll is high enough!).