I really hate whenever I try to explain how some bad rules can be abused and immediatelly get someone say shit like "If this happens in your group, change it" as if that would solve the problem. And whenever it is not soemthing you witnessed personally, then it means it never happens and could never happen.
By Exhaustion undercutting Rage, do you specifically the 2014 Berserker barbarian? That's the only one I know of that gets exhaustion from Rage, and it's up to them whether they want to activate that feature( Frenzy) or not.
Yes, it undercuts Frenzy which isn't good enough to deserve exhaustion. It was story based design that worked against itself.
Good thing they removed it in in the 2024 rules then
https://www.dndbeyond.com/sources/dnd/free-rules/character-classes#Barbarian
Woohoo, 10 years later!