There's no such thing as a "core hotspot". Intel, until AMD proved them wrong, used thermal paste between the CPU cores and head spreader, whereas AMD uses Indium solder, which efficiently transfers heat away from the CPU cores. Also, as you can see in the de-lid picture for the 1800X, the two CCXs, each containing 4 full cores (integer + floating point processor) each are in the center of the CPU package and soldered to the heat spreader, so unless you have a defective, warped cooler, or apply the TIM incorrectly, both of which you could visually see, you can't have a hotspot.
