If you instantiate multiple copies of the same transceiver instance using the 66:40 gearbox, the Quartus® II software will merge the multiple fPLLs into a single entity if possible. When this is done, the Quartus II software will report this critical warning on the fPLLs that have been removed from the design.
Yes, you can safely ignore DIV_CLK critical warnings reported for the fPLL used in the 66:40 gearbox ratio on Stratix® V GX/GS/GT FPGA and Arria® V GZ FPGA transceivers.