In a game about fighting, you'd think there would be at least one subclass for the player who wants to play the true glass cannon - with truly stellar DPR to compensate for being such a fragile frontliner character.
The crucial point is a lack of a feat to correspond to the fighter's -5/+10 feats.
Why not make it relatively simple to get your two sneaks per combat round? That's the approach of almost everything else in 5E.
Ranged rogue us assassin plus CBE. Apart from that ranged rogues a bit meh.
They don't suck that's a great weapon fighter having to switch to a bow or throw a single javelin.
People still underestimate Dex, utility, ranged, non combat and Rogues are Dex based.
I like the idea of giving rogues a different way to more reliably get SA, so they can use Cunning Action more often, but I don't really think Extra Attack is the best way. Not sure what would be a better (simple!) solution, though.
I'm not a fan of damage on a miss for sneak attack. It seems to go against the flavor of the ability (maybe I'm too old school there) and spells are still a finite resource. Cantrips are the at-will attacks and they don't do half damage on a miss. That seems like a more relevant comparison.How about changing SA so it needs to be declared before the attack, but it does half damage on a miss like the majority of leveled spells.
As a side note, even if wielding two weapons, you literally can not declare your bonus action to attack until you have made your Attack action and therefore know if you hit or missed. If you've already delivered your SA damage, Cunning Action vs. a chance for a small bit more damage is a much more compelling place to use Cunning Action.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.