Nikon 85 1.8 after owning 70-200 ??

hi guys, i am a happy owner of sigma 70-200 2.8. sharp lens btw.

recently, i have seen many great rebviews of the 85 1.8 g. my question is, do you think its a waste to buy 85 1.8 even after owning 70-200?? i am tempted to get one.

how is the dof at 1.8 and 85 mm focal length compared with 200mm at 2.8? which one will give me more blur? anybody had a chance to compare?

in addition, i also have 60 afs. so yeahh, i dont know. is it truly a waste to dump money on 85 18 afs?

thanks for your suggestions.