I think the fatigue system is alright now if you solo 2-3 star leves and have a moderate timeframe in which to play. Doing 5 star Dunesfolk, etc, can hit the cap very fast, but more casual play can take about 1-3 days to start hitting fatigue (which is fairly bad design, in my opinion... why penalize people for playing together to achieve a greater goal?).

The fact that fatigue can revert back after breaks helps somewhat, but I think it may become a more noticeable issue once new players are given a reason to actually play this game (i.e. fun).

However, the fatigue system becomes somewhat obselete after end-game is reached and the level cap is gradually raised through expansions, since the effect of the system becomes much less noticeable. Its main use is found in the initial levels in an MMO.