As Garotte suggests, the time to improve rotations and overall DPS uptime is now. If DPS is a struggle in T9, it will be even harder in T10+ since all FCOB fights incorporate timed mechanics that punish groups badly for low DPS.

You'll need to identify who is struggling and with what if you haven't already, or the group will not progress. Hopefully everyone shares the desire to improve and will be willing to act on constructive criticism.