Ruling on Psychic blades for Soulknife rogue?

The blades are finesse weapons, and it says it deals "1d6+ the ability modifier used to make the attack" and then 1d4 for the second attack.

My question is this, rogues have proficiency in Finesse weapons, shouldn't the attack look like this? (For a 18 dex rogue level 3, my current character) Attack roll + dex mod + prof bonus. Damage: 1d6 + 3+2. (since I have proficiency in the weapon type) 

I just want to check because that seems op... since I can then make a 2nd attack offhanded, easily resulting in 2 sneak attacks per turn with a +6 to + 9 or more to hit at higher levels.

Thanks!!

Proficiency bonus is added to attack rolls, but not to damage rolls. So you are +6 to hit (proficiency bonus +2, dex bonus +4 at an 18 dex). On a successful hit you do a d6+4, (weapon damage + dex mod).
Sneak attack can only be used once per turn, if you hit twice, or more, you still only get the extra sneak attack dice once on your turn. 

But you can sneak attack on other turns. For example, if the enemy provokes an opportunity attack. But even then, you’re +6 to hit, and d6+4, plus sneak attack damage. 

Since it’s a vex weapon, you can make a second attack, at a d4 damage, but that will use your bonus action, and rogues are usually better off using their bonus action to disengage and run away. But that’s a personal preference thing.

Okay thank you so much! I'm new to the game, and i see now where I messed up. that makes total sense, I thought I must be wrong it seemed way too strong.....

Quote from VizziniLamborghini >>

Okay thank you so much! I'm new to the game, and i see now where I messed up. that makes total sense, I thought I must be wrong it seemed way too strong.....

 I will point out as well that using your Psychic Blades also sets yourself up to use Sneak Attack in circumstances where you might not otherwise be able to. If you have no other source of advantage, and no allies near the enemy, the Vex mastery on your Psychic Blades will allow you to have advantage on the second attack so long as the first attack hits, triggering your Sneak Attack if you hit with the follow-up attack. This can be helpful if you have no other way to apply Sneak Attack that round, as it gives you a nice 1-2 combo.

Quote from Sequilonis >>

Quote from VizziniLamborghini >>

Okay thank you so much! I'm new to the game, and i see now where I messed up. that makes total sense, I thought I must be wrong it seemed way too strong.....

 I will point out as well that using your Psychic Blades also sets yourself up to use Sneak Attack in circumstances where you might not otherwise be able to. If you have no other source of advantage, and no allies near the enemy, the Vex mastery on your Psychic Blades will allow you to have advantage on the second attack so long as the first attack hits, triggering your Sneak Attack if you hit with the follow-up attack. This can be helpful if you have no other way to apply Sneak Attack that round, as it gives you a nice 1-2 combo.

Just to add on, the Psychic Blades have an innate Bonus Action attack so this combo can work on the first round if you hit on the first attack, the Bonus Action attack will be at advantage and qualify for Sneak Attack.

If you would rather use your Bonus Action for a Cunning Action or something else, you won't lose advantage from Vex until either you make an attack against that creature or your next turn ends so you have options.