have you had the card long? if so, try to re-apply thermal compound to the GPU & heat sink & kleen the fan.
if it's brand new, its your chioce to either check out the amount of compound on the GPU, or send it back .
in my travels i have found that the amount of Thermal compound applied by the Factory is barely enough.
To answer your question,, all or 98% of the heat should be in the heatsink itself. If the "card" is hot,,, heat transfer is in question.