Man, I wish Skull Mentors were 5D, but they are 10D (so 7D with hammer).
Still, as much as it pains me to admit it, you are probably just better off with 2D, against a skilled opponent. This places you more on the defensive though, with less mages in total no matter what you do. On the other hand, you can afford a bit more magic on your pretender, opening up extra options.
Honestly I think Magic scale is your hardest build choice for LA Ermor. Consider that you won't always be fighting in your dominion, and it all gets so complicated.....
(You'll not thwart me again, THEJEFF!
)