Did you use the thermal tape on just the GPU memory modules or both memory and GPU itself? I made that mistake and theres no contact from the heatsink to the GPU so it overheats as the thermal pads of 1.5mm are too tall! (at least on 27" 2013 14,2 models) I had to redo mine and just used quality 11kw paste which is non-conductive so no worries of short circuiting from spillage on everything. Temps are all good now.
Are you suggesting that you used this 11kw tape on both the GPU and the GPU Memory modules?
I brought that tape but 1.5mm is way too tall and chose not to use it after all on my 27' 2013 14,2 model. Instead used 11kw X1 Extreme Fusion paste from Master Cooler. Its non-conductive so don't have to worry about short circuits. Its also very thick so doesn't run. I used the "small pea" technique on the GPU and GPU memory dims. For the actual CPU which I upgraded from the base i5 to a i7 4771 I used the "Thin line" technique.