I also have had Dobies, and often they are everything you describe. They can also be jumpy, crazy, poorly trained, or just plain inbred and genetically screwed up and unpredictable. And unless it's a "service dog" no, you can't take them everywhere. Just like you can't take a gun in a courthouse, etc.
My dogs have been neither.
I had to have my police trained dobe put down Dec. 4th....it was the most heart wrenching thing I have ever done. Even on his death bed, his heart was telling him he had to protect me.....something I will never want to experience or do again under any circumstances.
His younger brother is still with me and has taken over his job of protection. Dobies are the most loving, loyal, family dogs you would ever want to have.
If Avishai, has had some unstable dobies, I'm sorry...you have to be careful of breeders.
Mine have been angels.......and devils if you dare treat my family with disdain.
r.