I don't know if the Dinotte is overkill, but if you care a lot about side visibility, consider the Planet Bike Blinky 7. Not as bright as the Superflash, Cateye TL-LD1100, or Dinotte, but it offers excellent side visibility (TL-LD1100 does too).
Honestly, taillights have become dramatically brighter over the years. It's far more important to have at least one that works than to worry about which one to get.