I can report I've been experiencing the same thing.

found a bug

I noticed OQ was displaying my hit incorrectly. I have 15% but it was showing as 10.3. I took at look and it appears to be due to the way hit is reported via GetCombatRatingBonus(). That value should be summed with GetSpellHitModifier() to reflect accurate spell hit for any caster who is getting their hit via expertise.