This surprises me, because my D300 and D800 do show actual Auto ISO in the viewfinder, before the shutter.
There must be a little more situation to the D7200 story? Auto ISO can change depending on how the camera is aimed of course, but hard to believe the viewfinder does not show it.
One exception was when using TTL flash, the older models (D300 and before)... the viewfinder always shows Minimum ISO value with flash, but after the shot, the LCD Exif might show new ISO flashing (only if needed for the TTL flash). Might change when flash triggers. If no flash, it shows current Auto ISO.
If speaking of flash, there have been three versions of Auto ISO with flash,
D300 and older DSLR stayed at minimum ISO with flash (unless TTL flash possibly might need more),
D800 and newer (ISO with external TTL flash might increase two stops, but internal flash might go to maximum),
and those in between (ISO goes high depending on ambient, regardless of TTL flash).
Auto ISO is always Minimum with a Manual flash, in any model (if flash presence is detected). Manual flash cannot react to Auto ISO.
EDIT: Ah so, the D7200 is itself an exception? I was not aware... Sounds like a mistake in design.