Didn't druid already get wildshape on a short rest? I do agree that barbarian Unarmored Defense is a bit lackluster though.
I get what they were thinking. Monk gets to add Wisdom because their awareness let's them dodge, so it should be roughly equivalent to let a barbarian add Constitution because their natural durability makes them harder to hurt. Dexterity being one of the main Ability Scores for monks throws this out the window though
Druids get two Wildshapes per short rest. Players just tend to not take short rests because they're not really incentivized. I know this because I read through the druid features more than my druid player did