I definitely think that IF Michael Schenker had a poorly cut nuton his Dean V's, he would have those same tuning issues on a Strat, SG, LES Paul, JEM, Iceman etc. if they had a nut with the same issues. I can see why the widely splayed Dean V head stocks can make tuning issues more prevalent and sensitive in the nut area/nut slots.
The key factor could be the angles that strings pass on certain guitar models, but it can also be the point of contact the strings make in the slots. If the factory or luthier does a poor job cutting and filing the slots, tuning issues are almost inevitable even with strings passing in a direct line to the tuning pegs. Friction ( dry or lubed slots), properly cut slot angles width, etc will all improve or cause a break down in tuning stability.
In Michael Schenker's case, I am sure that his guitar tech is highly skilled in fine tuning his nuts on his Deans, Gib V's or whatever guitars he performs with. We all should have such skilled masters of setups or work on our proficiency to do our own.
