yes.. excessive thermal paste will inhibit proper herat transfer.
Its pretty much beginner's screw up, the effecs can be rather significant..
The first time I tried using one of them gigabyte own thermal paste.. added like a good layer of it using a card spreader... then wehn I replaced it with just a small bead like punt in the middle and let the HSF pressure do its work.. my temp dropped like 3-4C..