I don't really know about the rogue being so out damaged by Barbarians and such, as in our games, the rogue seems to be fairly well holding his own. Oh sure from time to time when he can't line up a sneak attack or just flat out misses(he attacks twice and declares sneak attack on whatever one hits!) his damage might suffer but everyone has those sort of issues.
It would be nice if they added one of those nifty -5 to hit for +10 damage deals for our poor little rogue but if they did...im really not sure how often he would use it. -5 to hit is a HUGE deal in 5E!
As for action surge bah! Who needs it! It wouldn't help out sneak attack (but if it did Whooa boy THAT would be crazy).
Now I do LOVE daggers and so I would love some dagger feats! let me use a feat to add +2 to my dagger damage and I would be thrilled or even up the damage die from a D4 to a D6! Let me spend a feat to be able to use Assassin archetype specials on my Thief archetype rogue! (really only want the 3rd level one that lets me get advantage on everyone on later initiatives than I have on the first round of combat and a hit from hide counts as a crit.).
I think later on some of the meat we are looking for will arrive in the form of more feats and archetypes ect..
I'm sure my DM would let me do most of those things as house feats anyway. I'm loving Rogue so much more in 5E than in our pathfinder games.