Now I'd like to first state that I don't have the last gun for this yet.
However, I see these tanks in the game and I never thought they were easy to kill. I often felt that they were always killing me too.
My Hellcat however gets killed in 1 shot, and I can't kill anything with it. The gun is too weak, and the armor too thin. Maybe the next gun upgrade, which is required, will make a difference, let's hope so.