400-800 characters is kind of a broad range. I can see logic with each respective limit: 300-400 makes sure that you get either a nice bit of analysis, a nice bit of hype, or a little bit of each (best case) whereas some matches have enough hype and analysis to warrant a longer writeup. (Though, assuming that 10 characters would average to 1 word, 80 words does seem like more than a standard paragraph.)
The problem that I see is that the current maximum is twice the current minimum. If roughly-even writeups is a priority, then I would rather narrow the character range (difference between min and max) to 200, though I'm not sure where to hard-code the limit. I mean, Light likely doesn't warrant 800 character writeups, yet in most cases a 300 character Godlike writeup would be a mockery.
But hey, I don't do this regularly, so how should I know what's "good enough" per match.