talking of team balance, i feel nin/sam is a very strong combinaison, both boost each other and can cover for the other one. instead to say bring more ranged, bring a nin/sam in the group is far more interesting in terms of dps than bring 1 more ranged. that is definitivly far below in terms of dps. without forget sam have a very strong movement capacity. get away from a target don't stop them dps (enpi can be used) and they can be back to melee extremely fast.

i feel for the dps group a strong: brd/rdm/nin/sam is very good. in terms of dps and utility it will create a very powerfull group compared to most other group.
with this group, you will have 4 people buffed by slashing debuff, the nin vulnerability, the bard song, rdm buff (that mostly impact physical damage) and the sam dps.

you add an AST over this and enjoy the group that will be extremely powerfull