When your RMAd the cooler, did you check the thermal paste/pads on CPU to the heatsinks? I bet any new repasting may help; the PTM7950 mentioned above seems more useful as it should last much longer than thermal paste while still performing good heat transfer.
There’s a thread regarding the PTM7950 use here: [Honeywell PTM7950 Phase Change Thermal Pads/Sheets] Application, Tips, and Results