Hi Dusty, this is just my opinion, but years ago when I first started with archery gear I spent the summer shooting at one of those 24" or so offical targets with a yellow center, next ring red, next blue, etc... I was drilling the center shot after shot all summer, in those early days before I got wise and really started enjoying archery I was shooting a compound, hence the drilling the center ring time after time!!!
When fall rolled around and I got a few shots at deer, I bet I didn't get within 5 foot of the deer when loosing an arrow, luckly I did'nt wound any deer either. After that I started shooting at a big old sandpile behind my house, I would draw a deer sized target in the sand pile and then pick a spot in the vitals and spent the next summer like that (I doubt if they even made 3D targets in those days, at least I didn't have one...Ha!) Anyway that fall, 1985, I drilled the first buck that came my way.
Yes, I do believe that tennis balls or dots or spots become a HUGE cruch, just my opinion. I just got a new broadhead block a week or so ago, and the first thing I did as I do anytime I get a new block is painted the whole thing brown with a spray paint can covering those goofy spots and dots!!
I go to the extreme in that on my evening practice sessions I time it out whenever I can so that the last 10 minutes or so it is getting pretty much dark, and all I can see is the outling of my 3D deer or block, and no way can I see a physical spot on those targets in that light, so it forces me to pick an imaginary spot within those forms in the dark, and I can shoot everybit as good in those conditions as I can in broad day light, you need to force yourself to pick an imaginary spot withing a same colored live animal or same colored target, it won't happen over night though, and pulling it off in near dark conditions will take several months, but it will make you that much better in good light. Hope that helps, again, just my opinion. DK.