The below numbers are from my own group + ACT parses I've seen on forums. The ilvl listed is just the ilvl of the weapon, not all gear combined.

With ~ilvl100 weapon MNK should be 380-400; ilvl110 weapon should be 400+
DRG ilvl100 340-360; ilvl110 380+
BRD 340-360 (my best when I had ilvl100 weapon was 358 with 3 paeons used throughout the fight); ilvl110 380-390+ depending on songs
SMN I'm not sure.

Your MNK and DRG are not 'terrible,' but they are still somewhat low. Are they hitting towers or something? BRD is ridiculously low. No reason BRD should be below 300. Make sure they are popping their CDs whenever they are up (except Blood for Blood in certain situations).