Memory has basically never, ever needed heatsinks, ever, they are 1-2W IC's in general, RDRAM not necessarily required it but it worked different, it ran at silly speeds and accessed one chip at a time and they got hot, hence heatspreaders and not heatsinks, it was because they got localised hotspots. Other than that, I think some of the very early gddr4 got very warm, but in general cooling memory is more about appearing to be doing something useful rather than being required. VRM's, gpu's need cooling, memory not so much.
Most full cover blocks have a painfully stupid thick layer of thermal frag tape, its not even close to good quality thermal paste and is such a thick layer it does as much insulating as cooling.
