Life tap

Is life tap nerfed?How a lvl 80 with 3k sp gain 3535 mana with rank 8 life tap what give 3536 mana+sp scale?!

According: https://wowgaming.altervista.org/aowow/?spell=57946

health lost = 2000 + (spirit*1,5)
Mana gained = 2000+ (shadow spell power*0,5)