Whoopee, you're referring to the stick-on strips that attach to the inside vertical heel of the shoe, I assume, not the stick-on heel pads that lie under the heel. The latter would likely exacerbate the problem by raising the heel of the foot, giving it even less contact with the sides and inside heel of the shoe.
I have this very problem with a pair of soft Italian loafers. For me, even the rough suede-finished heel (vertical) stick-ons (or the sponge rubber ones) didn't solve the problem. I still got heel slippage. I tried adding a tongue pad. This helped a little, but didn't completely solve the problem either. I then tried sticking some pads along the sides of the shoe, running beside my heels, which did no good whatsoever. In the end, the most help seemed to come from tightening the fit in the vamp area, which the tongue pads aided to some extent.
So, I'm eager to see some answers here too!