reason why many use like duals or swords are mainly cause of Focus SAs and the added crit rates.
if you compare DPS for blunt vs sword, you will quickly start doing more damage with sword as you add buffs. especially in party with like sws and bd. reason for this is the amount of critical damage and rate buffs, even though you have less patk you still do more damage because of much better crit rate.
focus blunt is a good option in B and A grade if you can get it, but for S grade and normal hits a focus sword >> blunt.