That logic sounds flawed because how about the weapons with 246 attack rating? Like i said... they are capable of doing more damage when they have a higher impact. This also applies to high level mobs. 331 doesnt have anything to do with level 31. The previous cap of 300 also didnt have anything to do with level 30. Your starter gun has something like 28 attack rating. If you want you can use it through the entire game and it will always do the same damage. Maybe you are confused when you see different damage numbers on very low level mobs. I was doing a level 8 strike and my ice breaker only did like 1300 damage instead of 2500. But the enemies still went down faster than level 26. That is just bungie playing around with the formulas.