So I came across a homebrew archetype for Monk called Way Of The Lynx. The abilities at the higher levels are completely okay, but the one in question is the third level, Sneak Attack:

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> Starting at 3rd level, you have learned to exploit an enemy's distraction. Once per turn, you can deal an extra 2d6 damage to a creature you hit with a monk weapon attack so long as you have advantage on the attack roll. You don't need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn't incapacitated, and you don't have disadvantage on the attack roll. At levels 5, 7, 9, 11, 13, 15, 17 and 19, this bonus damage increases by 1d6.
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It follows the same ruling as the Rogue's sneak attack feature, with the same 1 d6 damage increase at the same levels as it does in rogue. 

My question is would this be too overpowered combined with flurry of blows and extra attack granted as a Monk down the line?

And does it make sense for it to even be the feature of an archetype without it being watered down in some way?