Vit drops on open RB, but no exp bonus?

so my question the same as title.. were farming today open RBs 93lv.. and average exp from RB is 1.4 bil.. if I have vit full means 200%, so it should be roughly about 3bil from RB if it uses vitality.. I dont say it drops fast, but it is decreasing and no exp bonus whatsoever..

Is this working as it suppose to work?