You are comparing shooting in war time, to shooting at stationary targets. Just because things are turn based doesn't mean the aliens are just standing around. They make themselves as hard to hit as possible. They would quickly jump out of their UFO, shoot and then run back in, giving only a moment for the soliders to have a chance to fire at this moving target.
For comparissions:
- It is not uncommon for paintballers to use 100-200 balls within a ten minute period. And if you are playing experienced people, it just means they are better at using cover so it is harder for them to hit.
- In real war almost all bullets miss. In the Iraq war one insurgeant was killed for every 250,000 rounds fired.
So yeah. The accuracy in the game is not very realistic. If you are figthing against fast, genetically modifed aliens like this, an accuracy of about 1% might be more accurate.
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The game is an abstraction of many things. When it comes down to it, the stats they have works for the balance of the game. It is challenging, and forces you to use tactics to defeat the aliens, without things dragging on for too long. That is the important thing.
And also realisticlly soldiers probably would have their max AP and strength when they arrive at x-Division. They would be as fit as they can get. But then their isn't anything to advance, and that isn't as fun.