Most players on this forum notice diminishing returns on Pie above 80-90, so if you have more than 90 points of Pie I doubt that's your problem.

I would definitely recommend Pearl Rings and a +1 weapon.

Wielding a +1 weapon is an automatic 5% boost to magic accuracy, which equates to almost two "free" Pearl Rings at the higher levels.

Scourge also reduces a mob's resistance to Umbral magic (like Poison and Bio), so you might try landing that first as well.