I use Distress in my game as a sort of catch-all condition, so it actually comes up pretty frequently.
Roll a nat 1? Distress.
Get reduced to 0 HP? Distress.
Lose a skill Challenge? Distress.
I decided to write "Exhaustion" in the subclass for accessibility, but the mechanics that apply to Exhaustion also apply to Distress.
I don't think you'd ever play this in a game with no Wilderness travel, like an urban setting. At least I'd warn my player before doing so.
But is the damage feature enough to be relevant?
Do you think I should look to the berserker and simply add a condition immunity instead of True Grit?
The point is "since Barbarians are all but immune to damage, conditions end up being one of their main weaknesses."
This subclass was originally designed to give the Barbarian player some options for dealing with those conditions.
For that purpose I was also thinking about adding to True Grit "if you are affected by a condition other than those listed, that would be resisted with a saving throw at the end of your turn, you can spend 1 Hit Dice to gain advantage on the saving throw."
Because I think there are some spells that are just effects and not actual conditions that would fall into what this subclass should be able to deal with.