All your points are valid, but it doesn't negate the argument that many classes have skills/spells that can seem overpowered at times. Let's imagine a world without symphonic echoes, or with a two-round timer - bashing giants/bearcharging rangers of the world rejoice. Distortion by no means seals a kill - in the example above, it was Gertabelle attempting to bash while convulsing that resulted in her death. I can also tell you, that as a bard if you go up against a Dolce or Woldrun and can't distort, well...yikes.

Long story short, symphonic echoes is a strong tool in a bard's arsenal, but to call it overpowered is just silly.