What is time dilation?
When close to a black hole, EMR VECTORS are altered giving us a relative time reading.
Time itself does not change.
Note from my original question that I'm referring to a measurement of the object's orbital velocity or period as it would appear to an observer "far away" from the black hole.
From other comments, the velocity or period would appear slower. And thus to correctly calculate the black hole's mass based on the closely orbiting object requires a calculation based on GR.
My next question ... Let's say you discover Object1 in an apparent "slow" orbit around Object2. Wouldn't you be mislead, by that apparent slow orbital period, into thinking that Obect1 is orbiting a "low mass" Object2?