Hero spellcasting chance keeps droping

Is it intetional to for experementalist perk to raise more often than methodologist after you cast a spell?

I have like + 10 to ritual with equipment and i remember i could cast a lv3 spell with 20% chance of success, after some battles i dropped to 40% for a lvl2 spell.

Also experimentalist dont reduce cost of spells for warlock class.