Quite sure the change was made for 2 reasons:
1. Deep dungeon balance. Riddle of Earth's damage reduction is good currently, but when you try to use it in solo instances, you'd start realizing how weak it becomes in a very drawn out fight. This only becomes more apparent once you reach higher floors of Deep dungeon solo. However, the previous Riddle of Earth would be comically broken in damage mitigation bursts for themselves if MNK has to take a hit every now and then.
2. The increased cooldown is to balance MNK from being too strong in personal self sustain in relation to other party members and including the existence of healers for party content. Having a 500 potency heal on top of a 20% mitigation every 30 secs is pretty ridiculous.


Quote Originally Posted by Rollout View Post
Nature's Minne is now a more powerful Mantra, so it's not even unique. Mantra also only works on GCDs, whereas Arcane Crest just broke and provide a HoT to EVERYONE rather than just the Reaper.
Yes, it makes sense Nature's Minne is a more powerful Mantra. After all, one of them is literally made to be a support class (physical ranged DPS). The fact that MNK still has support abilities on top of its DPS on top of its higher DPS performance is pretty telling tbh.
Last I checked, No, Mantra also works for oGCDs because it affects healing actions (all abilities and GCDs), not healing magic (spells). Subtle difference in text, but a huge difference in gameplay. This means Mantra also works for Riddle of Earth. So for solo play, mantra can give a 50 potency buff to Riddle of Earth and an additional 50 potency to second wind.
Arcane Crest is not more broken, it's just more easier to use in general after the nerf. However, skills that apply % healing to all abilities can be stronger when used by healers who benefit entirely from it, including other jobs who have healing utility like Arcane Crest. It affects their healing and their shield potencies - which can make a difference for raidwides and vastly increase potencies the more skills are used in succession. So abilities like Mantra and Nature's Minne simply get more powerful the more healing is required (works better for burst healing) compared to something like Arcane Crest - which is more stable regen.