Well, there's your problem - you tried to optimize Rogue damage numbers without understanding how it works. If you had the Rogue use TWF, they'd deal quite a bit more damage (since they'd get two attacks, upping the chance that they'd get to apply their sneak attack damage).
Also, here's the thing about your wider criticism... you're ignoring the rest of both classes and the side effects of how those classes deal their damage. The Barbarian deals better damage, but they're stuck with melee range and are giving their enemies Advantage to hit them to do so. Meanwhile, the Shortbow Rogue deals their inferior damage to more-or-less anyone on the battlefield, and has defensive tools that make them hard to profitably get rid of for Team Monster (on top of explicit defensive features like Evasion and Uncanny Dodge, being able to Hide as a bonus action makes it tricky to target them with stuff). The Rogue is basically a transferable DoT, and that's leaving aside subclass-derived utility (like the Thief opening up Healer shenanigans or the Mastermind handing out Advantage on attack rolls).
Would I complain if the Rogue got Cunning Strike, though? Nah. I miss Ambush feats...