|Class is in session.|
Which means that you have a 72.2% chance of rolling a 6 or higher to assault as 7 is the most common result from two dice being rolled, not 6 as you were just thinking - and here's why. Remember that for the throw of a single die, all outcomes are equally probable. But in the throw of two dice, the different possibilities for the total of the two dice are not equally probable because there are more ways to get some numbers than others. There are six ways to get a total of 7, but only one way to get 2, so the "odds" of getting a 7 are six times those for getting "snake eyes". This simple example raises the idea of distinguishable states. For example, throwing a 3 is twice as likely as throwing a 2 because there are two distinguishable ways to get a 3.
With 'random charge' ranges you actually now have a 58.4% chance of getting 7 inches or better out of your charge. Will there be days when you are in the 8.4% of the curve who gets off a three inch charge when you need six? Yeap, there will be, but if your whole plan fails or succeeds on one assault you might have a few other things to address with your army. That being said, there will also be days when you need an eight inch charge and manage to pull it off - something that would have never happened in 5th.
Why random charge ranges? Because they fixed rapid fire lol, like duh - and stuff. Well that and shooting someone in the face and running up and punching them in the face are two totally different things, which is reflected in how fast they get up there to do it. It is also reflected in assault guys, who regularly run up and punch people in the face, can re-roll theirs.
The dice Gods may be fickle, but in this cause you still have math on your side. And math tells me that getting a six inch assault will still happen 72.2% of the time. Nothing game breaking there, so calm down grab a mojito and repeat after me - 'everything will be A-O-K'.