15 years growing in ohio, deer definitely the biggest problem. We've been able to obtain nuisance permits from the state in years past, allowing the harvest of deer out of season. Something to consider if you have the time to hunt. If our roots can make it to 5 years, I find that they can survive repeated browsing.
In a normal year here, the deer have eaten half of our plants by mid June. By the time we are digging they have browsed about 80 percent of the plants. I am often digging stems. This also makes for very small 15-year old roots.
I think the Deer here have developed more of a taste for ginseng over the time we have been growing. It is now a preferred food source for the local herd.
I have experimented with running 100# test fishing line around major planting sites and this seems to help. When the deer walk into it it discourages them. Also they won't typically put their heads through downed tree tops or brush. Planting under downed tops or putting woody brush over your plants is a good way to protect them.
Don't give up, the plants will come back even if they have to take a couple of years \"off\" after being browsed. We're just making the deer \"medicinal\" and need to eat more of them.