PSO2 class builds generally fall into 1 of three types. Either they excel at single-target DPS (bossing), Area of Effect (mob crowds) or they excel at neither as they aim for a balance.
At the end of the day however, everyone except for the balanced build has a weakness. So while your Braver friend may be taking down bosses with minimal effort, if that boss produced loads of mobs then your friend would really struggle to clear them out. What really matters in PSO2, as with any game, is; "Am I having fun?"
If you have the ultimate one-shot build but find it tedious and dull, then play something else.