i have a weatherby 30-06 with a nikon prostaff 3x9x40. Most of our shots are going to be in the 75 yds - 150 yd range. Max will be 200 yds based on recent hunts. My son is on me about upgrading the scope to something with more magnification (4x12) and better glass. Do i need more power in my scope?

would appreciate any input. We are "accurate" with current set up but not "overlapping holes in paper" accurate. I feel this is more due to the shooter (me) than the scope. But i want to get tighter in my shots. Thanks in advance.

Switch to diamond zero target so that you get a very repeatable aiming point, with a circle, how can you be sure you're holding in exactly the same spot each time? The diamond will shrink your groups.If you can hit an eight inch paper plate every time at 200 yards you're accurate enough.
As far as increasing magnification, if your power setting goes up, your field of view goes down. You need to consider that a deer may only give you a couple of seconds pause as its moving, you need to find it and shoot in that time. Higher magnification works against that.

If your max is 200 yards then you probably wont need more magnification power in your scope. I would just suggest a scope with the best optical clarity, and for that I would recommend Zeiss & Swarovski.

I like to use targets that have 2" or larger square blocks on them. I place the crosshairs right on the corners as my precise aiming point, and shoot the 4 corners for groups doing load ladder workups.
Only time I use a round bull is for initial sighting in on paper, then move to the square blocks. I've got a bunch of really old round 1" black target pasters I'll stick a smaller 1/2" red round paster on top of to shoot for groups at longer distances than the load workup distance.
Ron