I'll concede that the TWF rogue does more damage than the monk, as long as you concede that the monks damage is close to that rogues. That the damage is close is important for my next point - stunning strike and open hands prone will be enough to close the gap and then some, ultimately putting the monk ahead in damage. Which I think brings us to your next point...
I mean the basic problem here is we don't know what the party composition is. Have another primary melee person in the group? Have widely spread out combats? Have casters who force lots of Dex saves? Have casters who target other things?
As examples:
Have a great weapon fighter or hand crossbow shooter in the party with a Monk? They're going to do a lot more damage.
Have a blasty Wizard who does a lot of mass reflex save spells? They're going to do more damage.
Have a non-blasty Wizard who tries to incapacitate targets? A monk+that wizard isn't a great combo.
Finally, Rogue 1/Monk X is a great multiclass, simply because it solves the 'So,who is the party Rogue' problem without really disabling Monk capabilities.