Tireless rage at 17th level removes the tirdness of the rage; but yes I agree it is a pretty harsh bonus only removed at endgame.
If rage were to last for 1 round PLUS your constitution bonus or something you could extend your rage significantly enough so you are fatigued less in most longer fights - but still enough to make Tireless Rage feat still viable.
on a pure amusing level... the fatigued aspect made the barbarian in our campaign have something to rage about :P
This actually reminds me of the time I was playing AD&D and we rolled "evil" characters and went on adventures against good aligned creatures and the like.
What made it different was our GM did something different - he did not adjust the difficulty of the encounter but made our enemies work in co-operation and as a team.
Advancing into a dungeon dealing with well thought out ambushes traps, archers targeting spellcasters; and went we went out the dungeon to heal - they did likewise strengthing their own defences against raiding during the night so we could not rest for spells.
The good 'party' was 'sub optimal' as well; no casters only fighters & rogues and 1 captain with a magical weapon against our pary of a cleric, mage, fighter and a thief
In much the same way I have noticed from watching a couple of playtests is they all struggled initially; but they become more efficient when they started to do things like raise shield+shield block flanking and using the terrain to their advantage they progressed much faster
It was no longer just 'I charge in with my sword raised and slice off a couple of heads' but - hold on... how can we work things to our advantage.