True.

So, you're doing D6+D6 from dagger, martial arts from your other attack (unarmed), then flurry - and so it lowers the dice at higher levels - but it remains good. Also, you're making up this damage from Empowered Strike - for example - as a subclass feature. It does make it so that, particularly at higher levels, unarmed is better - but unarmed is going to be better (generally) anyway because force damage isn't resisted.

So, you're trailing by one when the die changes to D8, trailing by two when it changes to D10, and by three when it changes to D12 - on average. However, you're gaining your ability modifier an additional time - which will counter that average reduction. And it's an extra hit roll, sending down your chance not to cause damage at all.