I just fought my first 2-3 dragons and I'm wondering about the meaning of being able to target each leg or the dragon's head. For me all those 5 targets always have the same health bar. So actually what's the point of this?
From my experience it just slows them down and seems to prevent them from flying away. It also lowers the amount of damage you take from it's various attacks.
It's not possible it seems as I have tried myself. The only change is how the health bar lowers on each leg, or other part of it's body when you attack it.
My favorite part is destroying the legs of the giants as they will fall down.
So really it all comes down to just another bad design decision by Bioware.
There is a point actually. If you target a certain leg enough, they'll topple over for quite some time, during which you're free to go all out on them. The same thing goes for giants.