Is Fresh Air not working?
Yes you need to proc a crit outside of air to recharge it. It’s not that it’s misleading; it’s just that the trait was introduced long before overloading, where the class didn’t have a timer while still being in air. And yes, the ferocity bonus is temporary, mostly to prevent it being in effect whenever overload air comes back up.
Brynsear answered your question really well, but I will add that the standard fresh air build + rotation for both D/W and (less commonly) Staff does in fact spend virtually all of its time in air attunement. You swap out of air only to you your highest priority 1 or 2 skills, or whatever utility skills you need to use, and then immediately swap back to air. You will rarely spend more than a second or so outside of air attunement at any time.
There are plenty of youtube videos showing the fresh air dps rotation.
after you complete the overload, you swap, start the casting of a powerful skill, and swap back while the skill is casting, spending only like half a second out of air, and you have the ferocity bonus up while the AoE from air overload is hitting things on top of your hitting things with your active attacks. ie massive damage