Fangs of Fury is not modifying recycle, unclear as to whether the delay modifier works or not (probably not working either). Affects both the crystal and the AROP headscale.
This is easy to test. Ravage has a 2 minute recycle = 120 seconds. 5% = 6 seconds. So, after using the Ravage attack, hovering the mouse over the ability, shows how must time is left until it can be used again. Seeing 1:59, 1:58 etc means it is obviously not working. If it was working you would see nothing higher than 1:54. Myself and another few other dragons all tested this, it doesn't work for anyone. This effect should work whenever the crystal is equipped, not just when the fang of fury effect is on you (It doesn't even work then).
Primal Rage crystal does work for spells. Even easier to test since Drulkar's Wrath is 10 minute recycle = 600 seconds, 5% = 30 seconds. Once casting it then seeing 9:29 left it shows it works.
Also, the Quickbreath effect on blighted headscales (and maybe other scales), which comes in -10% recycle and -20% recycle variations, do not work either.