Not 100% sure that's the spellpower thats bugged.
The numbers in your test pretty match MCL being borked.
Before you had MCl10+3(savant)+2(TOD)+3(destiny) right? If we assume that now it's cast with MCL 10 the numbers match (not exactly but close enough). Same thing with Chain lightning MCL28 dropping to 20 (match a little less well but we don't have a huge sample of numbers).
Repair spells and MM still hit for the same amount right? Both would not be affected by MCL being borked (unless you have a staff of power).
Doesn't explain the crit difference looks like lost about 0.5 crit multiplier. Wether it's because items are not applying their lore or the base crit multiplier got lowered need some changes.
Guess what casters are the least affected... Shiradi, that don't care about MCL anyway. Still affected by the crit change though.