If you have to look and try to figure out if he is wide enough then he is prob too close to shoot anyways.
Have you tried grunting or something like that to get him to stop?
The Shots I have been seeing are in the 150-180 yard range - not a extreme distance but still far enough away to need some kind on magnification to get a idea on rack size & width . If deer is coming either toward or away from you makes it easier to judge . The 2 deer Saturday were side profile to me and traveling, I could only see one side of the Rack.
I know in East Texas we use to "whistle Stop Deer" for a quick shot.( under a 100 yards)
Having a Grunt call & trying to use it to stop a deer - I don't know , seems you would be using up time and having your hands busy with the grunt call & it still wouldn't help if he stopped behind the mesquite/cedar etc
May try a "whistle Stop" but not sure at 150-180 yards out how well it will work but it at least something to try.
PS A funny incident happened to my hunting buddy last weekend - in a blind 3/4 up the side of a mesa looking a 2 feeder's in a Bowl shaped area . decides to try rattling a Buck in and it worked to a degree . Buck came in from top of the Mesa to the back door of the blind and huffed & puffed & snorted from 3-4 feet away from the back door and made my buddy almost chit himself.