well, after getting 25/31 on main and 22/29 on second i can give some thoughts about new raid

light souls (blue one) can drop from normal raid, but the probability is like 50%, mb 60%
expert almost always drop blue soul, i had only 3 times when it dropped devil one
ragnarok can drop 2 souls, one devil, second can be any, but i got 2 souls only on ragna that i started myself (needless to say, i was mvp there)