@Jack, my members and I practice bombers against our own GBs. We can down each other with 2-3 bombers still.
You're right though, it takes 3-5 average bombers to take down a SKILLED GB pilot. Did you know it takes 3-5 bombers to also take down a SKILLED Cruiser or Battleship pilot? Thing is, there aren't many of them. So you THINK it's easy to down BS pilots with bombers but hard to down GBs. But in reality it's just easy to down noobs and hard to down pros.
If any balance needs to be made, it should be to zoom, not the ship stats.