This sounds about right, depending on what you are mining you can even decrease the power limit some more, i've noticed that if you're mining ETH your power limit could be very low (60% maybe) and it won't affect performance, but for something like mining digibyte or zcash this would affect performance, sometimes its better electricity wise though, i have my 1080 on power 70%, core +99 and mem -300 , i'm mining digibyte with ~600Mhs