We just spent 10 days in YS, hiking the back country. IMHO, seeing Elk, Bison, Deer, and an occasional Moose is not really a problem in YS. Chances of seeing any Bear these days is really rather remote, especially a Brown bear. If you want to see Bears you will have much better luck in Denali National Park, Alaska. And, oh yes, I do know it's just a little bit further to travel
). We saw several Bears each day we were there, some very close from the truck--like a Brown bear mother and 2 cubs 30' from the road).
PS- in West Yellowstone there is a wonderful Brown bear and Wolf sanctuary where they have the rescued animals in large enclosures interacting with other members of their own species. It's very interesting to see these animals interacting, some actually playing/wrestling each other in the large inclosure water pool.