While rich in substance, the lack of distinct form is what describes Miraar best: They are shapeshifters. In their 'true' form (if such a thing exists for these creatures) they are mostly unremarkable with regard to wit, speed or strength. In fact, the single distinguishing feature of these human-sized and human-shaped beings is their 'blur' - the fact that however hard you may try neither outline nor detail appear fixed.
Once a Miraar shifts their shape to match someone else's, they partake in that persons physical characteristics and mental strength, making it almost impossible to distinguish one from the other. Yet knowledge, learning and memory are not transfered, thus forcing a Miraar to learn and train as much as everyone else.
As the Miraar's ability to change their shape into those of other creatures developed over the course of the ages, in turn the 'true' form became more and more a stagnant placeholder. It does not grow in the same way that other races do, dependent on profession or luck. Instead, it will remain at a low, only slowly increasing level of balanced characteristics at all times.