18+ dice isn't really that broken, considering that such dice pools are usually opposed tests, that are subject to multiple negative modifiers outside of the most optimal conditions.
Shadowrun is a game where the overall power level can vary a lot, although effectiveness is not something that always equates to combat ability. Even in the core book archetypes, there is a world of difference in the dice pools that the street samurai has, compared to those of the bounty hunter. But the street samurai can shoot things, hit things, sneak, and drive, and that's about it. The bounty hunter has a much wider skill set. He can change a flat tire, patch up a wounded comrade, pick a lock, scare someone into cooperating, and so on.