With BLU you can see how it will destroy the balance in low level dungeons.
A level 60 Blu at any 60 boss feels balanced.
But at low level fates he just facerolls everything, even without 1000 needles.

And the potency difference between level 60 and 80 skills is even higher.

It would be nice to have but it takes a ton of work to balance all skills to a lower level.

Also, if I were any starting newbie, I would get excited for the endgame if I would see all this awesome skills that would later be available to me.
It would give hope for better combat in this early 2.5 gcd 1-2 combo part.