On insane, they pretty much are perfect yeah. But they're supposed to be, and changing this would affect the balance of all existing missions - retail included - and as such there's basically no chance in hell of it happening.
Also, it is actually still quite possible to evade much of their fire on insane. The thing to keep in mind is that they're perfect at hitting where they expect you to be, ie. they shoot at what would be their lead indicator if they were a player, so if you're flying erratically enough they'll still miss despite their "perfect" accuracy.
Some things to try that might help are to first of all make major control movements when evading, not just little turns and jinks - You need the course change to be significant enough that you're at least a ship's length away from where you would have been if you'd continued your original course. Further, try to constantly vary your speed by using short afterburner bursts, and using rolls and slides (where available) in combination with everything else to make your flight path even more unpredictable. Once you get a good evasive pattern down, you'll find that insane isn't that bad. You'll still get hit, but far from with every shot.
Of course, there are exceptions, such as when fighting at point blank range or when flying certain ships. When flying an Ursa, for example, there's nothing you can do. A ship's length for that ship is just too far to be able to get out of the way given its lack of speed. But for fighters, with enough practise, you should always be able to avoid a lot of fire even on insane.
