Two-weapon fighting is very appealing to Rogues, and probably brought up in all the character optimization builds. It's the reliable way for a Rogue to get an extra attack.
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.
Problem is, outside of Haste, it's bloody difficult to set up consistently, even for a moderately accomplished minmaxer.
But it proves that the Rogue is indeed underpowered. In games with feats, that is. (The Rogue is probably quite good in games without feats)
Sentinel and Mage Slayer both provide extra chances for opportunity attacks. I've never had issues getting my rogues into position to take advantage of them frequently. Making enemies want to get away from you is pretty easy, since you can drop level appropriate enemies with 1-2 attacks pretty frequently. If your game doesn't involve fighting spellcasters very often, Mage Slayer drops in usefulness, but I've never seen such a game, since spellcasters are the most challenging enemies.
Even if they use their spellcasting to get away from me via teleportation, that's fine, I'll get to them again next turn, and they'll either burn another spell slot on survival rather than offense, or they'll die quicker from my OAs. Either way, I'm contributing an extremely great benefit to the team's success.
A vicious rogue subclass might be one that simply changed reaction attacks made by the rogue to always resolve
before the triggering action resolves. Then Mage Slayer gets you an attack even if the enemy teleports away from you.
Of course, an archer rogue is gonna want to go Stealth mode with crossbow expert and/or skulker. There's a trade from turn to turn between stealthing and getting a second shot, but that's fine in this case. They fill in eachother's weaknesses. When you can't get stealth at all, you just shoot as much as possible, and when you can, you only use that bonus action shot as a back up for when your Advantaged stealth shot fails. Or, if you don't like such tradeoffs, you just pick between being a stealthy sniper and being artillery.
I'd also love to see a rogue subclass that is part Artificer, and gets to fill arrows with alchemical items, like arrows that deliver the damage of a vial of acid or alchemist's fire upon impact, or create a 5 ft radius obscured area, or an area of difficult terrain like a half sized web spell, or save vs blindness or deafness in an area, etc.