Rogue's Sneak Attack is Oddly Limited

its only 2 times a short rest, and that assassin rogue can guarantee a crit once a short rest at level 20. But that is level 20, and giving the rogue a specific damage focused sub class while the fighter does not. At most levels rogues do not have a auto crit option, or a double damage on a failed con save in the first round option etc. At lets say 13th level which is a pretty normal end point rogues are just hitting for 8d6+dex mod with a short sword. So like 33/34 damage on average. A fighter is hitting 3 times for 2d6+5 without feats, so 39ish. But feats help them more, magic weapons help them more.

But fighters and rogues are not the only martials. A barbarian is only hitting twice for 2d6+8 or 30ish though likely with advantage on the attacks. Against a low AC enemy they will likely get 1d10 more on 1 attack so 35ish damage. 

Now heavy weapon mastery exists and as far as I know there is not a rogue equivalent feat so at 13 another 5 damage per hit which does push the barbarian past the rogue.

Monks at 13 will be hitting 5 times for 1d10+5 which I am told is terrible online. optimizers if they can't find a gimmick to push damage to infinity it sucks.