I don't understand the criticism that supposedly Mavuika is too perfect

Because she's not. She clearly has a blind spot about her own emotions and feelings. As shown in the Archon quest she hides behind her sunglasses when she wants to cry implying how uncomfortable she is in showing emotional vulnerability. She redirects the focus onto the greater task even though she does have unresolved inner matters. That's not a sign of balance or perfection.

She probably is quite close to perfection when it comes to duty, power and empathy for others but her own sense of self preservation is extremely low.

If you want to make a case that it's exactly because of those reasons that she's perfect (willing to sacrifice her own well being or even die for the sake of everyone else) then I guess you could. But if we see perfection as something that is inherently balanced, she's not. Her energy is expressed almost all of the time outwardly.

How do you feel about this common argument that people make about Mavuika?