I am rarely having wireless charging problems with my N8 in a thin Spigen NroHybrid case, although I have the convertible Samsung promo charger, which can be finicky,. Occasionally, charging turns off, a minute after placing it vertically on the charger, especially if the bottom edge of the case isn't touching the lip on the inside ledge of the stand. In addition, the phone's home button needs to be perfectly centered over the blue light of the charger.
It is interesting that my wife's LG G6 charges without a hitch on the Samsung charger, but won't charge on a Seneo charger unless she removes the thick case on her phone. However, she accidentally discovered that her phone, even with that case on, will charge if the phone is placed upside down onto the Seneo charger. The Seneo charger works fine with my N8 in any position.
So perhaps, if you are having problems with your tall N8 on the Samsung charger, it might be worth trying to charge it vertically upside down. It just might make it easier for the coils in both the charger and the tall phone to "see" each other.