You need fairly expensive equipment for that. Flutes are pretty damn loud, esp in the higher registers and cheap mics do not like that. Believe me I tried. :X
Also, while hearing yourself from an audiences PoV will certainly help (instrument sounds different if you play it yourself), it does not give you intricate feedback on WHAT you need to change to get the sound you want. You only know that this ain't it.
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Typically by having obviouse class mechanics.
EG: FF-XIVs mage has a buff. That enables you to cast your main damage move. So aiming for a maximum uptime of that buff while optimizing movement etc would be possible w/o any log at all.
What wouldn't be possible would be obsession over secondary stats because you had 0 information on that.
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Shadowpriesting on Dr Boom in Netherstorm! Man the memories.
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By seeing that the best of the best fail hard.
Who is the best? Typically players that progress very fast.