Have you looked into
-Intermittent Explosive Disorder
-Borderline Personality

Unfortunately you left behind a big mysterium of what exactly you do when angry so it's hard to imagine what exactly is causing you problems with your anger issues? Is it that you hurt other people or do you just yell at them or insult them, which causes you to regret afterward because it strains your relationships? Might sound hilarious/banal and off topic, but I was very aggressive until I got about eleven years old. So I have a vague idea of how you may feel. I think in some weird twisted way I profited from being a girl, because as a girl, it is seen even more socially inappropriate to be aggressive. That way, I was almost "forced" to direct my rage in another way. So today, I rather have symptoms of turning bad feelings/impulses inwards/against myself. I still have huge anger issues, but they aren't so easily visible on the outside. That's good because I am better able mold in to my social environment.

I see what you are about. I think this is not just a thing about therapists, but about people in general. There are few persons who seem to get how sickening, outraging, disgustig and annoying it is, if everytime you tell them about a problem of yours, they start to relativize, deny or downplay the problem. I think that this kind of behavior is related to some kind of (maybe even unconscious?) aggression. People don't want to accept your problems, because that way they had to accept there is suffering in this world. Also it can be frustrating to realise someone has a problem you yourself can't understand at all.
Hm, anyway, I'd suggest you that next time a person plays down your anger problem, tell them exactly what you wrote in here. That it makes you angry, that they don't understand, that you feel they are unempathetic.
Hm, the last thing that comes to my mind, "numb" feelings" and "unpredictable" rages sounds to me like you are dissociating your feelings a lot. That would cause your inner "landscape" to be pretty unintegrated and therefore explain that you have at one time problems feeling emotion and another you are overwhelmed by them.
Hope some of this has been of benefit for you!