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 and Arria® V GZ transceivers. If you instantiate multiple copies of the same transceiver instance using the 66:40 gearbox, Quartus® II will merge the multiple fPLLs into a single entity if possible. When this is done, Quartus II will report this critical warning on the fPLLs that have been removed from the design.
Device Family: Stratix® V GS, Stratix® V GT, Stratix® V GX
Area: Component, HSIO