I have planted thousands of Norway Spruce with survival rates in the high 90 percentile range. I have never caged one and some years I have experienced browsing of all the previous years' new growth but they do seem to catch up within a year or two. Once we stopped winter feeding where we kept unusually high numbers of deer around that problem pretty much went away. I haven't planted a bare root conifer in many, many years. I plant the size 10 plugs with excellent success.
I have never had a plug pulled out of the ground when I planted them with my homemade plug planter. I have, however had some plugs pulled up when I made the hole with an auger. I have never had a deer pull up a plug that I am aware of, but I have had skunks pull them up.
The plug planting tool makes the perfect sized hole in the soft spring ground...
After the plug is planted there is no loose dirt around the hole. You would never know (nor would a deer) that the tree had been recently planted.
But when you use an auger to make the hole, there is a lot of loose dirt around the base of the seeding tree. I believe that this signals to a skunk that perhaps another critter may have buried some type of goodie there...
So they dig it up to investigate... These plugs were clearly dug up by something other than a deer.
Skunks also like to dig up my freshly planted oak seedlings...
But when I trap the skunks out - nobody digs up my trees anymore. This is only my theory, of course, as I have never actually seen skunks digging up a seedling tree, but when I have had trees dug up, I get the traps out and the problem goes away.