Dragon Ball Xenoverse: Guide to Finding ALL the Dragon Balls [PS4-Xbox One-360-PS3-PC]
The Dragon Balls are a very rare loot in Dragon Ball Xenoverse that is dropped by other patrolmen, which can be either randomly generated enemies from the CPU or characters created by other players who "invade" your game to fight you.
Dragon Ball Farming Guide
These patrolmen can appear in most parallel missions, in the form of NPCs with which you can interact and possibly challenge after clearing an area (not infrequently they will attack you themselves after you have cleared an area). In any case, before facing these opponents it is a good habit to check their level with the scanner because, in a completely random way, you can find yourself facing level 5 fools but also level 80 monsters.
According to the first information gathered on the net, it seems that by far the best way is faster to find Dragon Balls is the Parallel mission 15, where you fight Freeza on a dying Namek. You will need to be very powerful, as the faster you defeat Freeza, the more likely you are to blow up a patrolman after his death.
Let it be clear that, even in the event that the patrol boat jumps out and you manage to kill it, Dragon Ball drop is never guaranteed. The big advantage you will have by trying it exclusively in this particular mission is that it only takes about 2 minutes to complete, so you can try again over and over again dramatically increasing the chances of getting all 7 Dragon Balls in no time.
Also in the parallel mission 15 there is another way to face the patrollers continuously without wasting a lot of time and without having to defeat Freeza.
Right at the start of the mission, use the scanner to look for a time patrol in the first area. If you find it, approach it and challenge it, otherwise start over and repeat until one appears. After defeating him he will drop a Material or a key element, the latter often being a Dragon Ball. Again you need to keep trying, as Dragon Balls are and remain purely random loot. From what the users who are trying it report, it seems that it is possible to get up to 5 spheres with this method.
Finally, I also propose a video that shows how to get the dragon balls by playing with other players