I think a split mechanic may be the best way to go ultimately.
The problem going on right now is that the Rogue's SA damage is stacking up pretty aggressively. Now we don't know if he will continue to get a d6 per level, but you could make the guess based on 5 levels of example.
That damage seems to scale way past what other classes are doing.
The counterpoint is that the damage requires actions like hiding so you are really only dealing that damage every other round. That would work as a balancing mechanic as long as getting advantage is fairly difficult.
However, that is a tenuous position to hold to. With the future of new mechanics and spatbooks, it highly likely rogue's will find it easier to get advantage in the future, and suddenly their damage goes through the roof.
So if the SA damage is going to remain that high, I think additional restrictions need to be put in place, which might ultimately lead to "two" kinds of sneak attack with different rules and different damage pools.
So let's say a standard attack in the weapon you're best in does about 1d8+3 to 1d10+3 damage per round, so on average about 8 damage.
A level 5 rogue gets 6d6, or 21 average damage from Sneak Attack.
A level 5 fighter gets 2d8, or 9 average damage from Deadly Strike.
So a rogue going all-out against one opponent deals 29 damage with SA and 8 without it, while a fighter deals 17 every round.
If the rogue alternates using an action to hide and then Sneak Attacking, he does 14.5 damage per round average, significantly less than the fighter who just stands there and attacks.
A rogue needs to spend less than 41% of his actions hiding (and all the rest Sneak Attacking) to get up his average damage per round to rival the fighter's. This means that at least once every 5 rounds or so, the rogue has to be able to Sneak Attack two turns in a row, due to ally help or circumstances.
(This is all ignoring chance to hit, which gets too complicated for me to calculate with Advantage, but is probably a net advantage to the rogue except against extremely low-AC enemies, since the rogue's lower attack bonus is more than offset by the amount of attacks with advantage he gets.)
And just for contrast, the level 5 wizard can Lightning Bolt (6d6=33 average damage) a couple times a day. So the martial classes really do outshine casters in single-target damage, while of course that one 5d6 Fireball or 6d6 Lightning Bolt is more accurate (targeting Dex not AC), more reliable (half damage on save), and can take out a half-dozen or more enemies in one shot.
LONG STORY SHORT: Right now rogues are slightly less damaging than fighters when they get a sneak attack every other round, although all those attacks with advantage probably make them close to equal (since the rogue is overall more likely to hit).
If you use the time-honored and genre-appropriate technique of hiring two commoner NPCs to walk up and stand next to enemies while your thug rogue archer snipes them from 50 feet away, of course, you can sneak attack every round already.