I never get this mystic coin threads. You are making legendary, you know which materials are used for it, you know how expensive it is and that mysic coins are a part of this expensive crafting list. You can earn them in game(login rewards, anomaly event, mysic forger daily, CM fractals, daily fractal chests), you can buy them from TP and their price has been very stable for very long time (~1-1.2g/coin). How are they problem exactly? When you are going to craft craft legendary you can easily tell how much gold you will need to sink for mystic coins, like with any other material. I've crafted over 10 legendary items and mystic coins are never issue because I trea them as part of the overall expense and there has never been issue with availability. World completion, gift of battle timegate and account bound materials are way worse than this. In my opinion mysic coins prices are in sweet spot right now, not overly expensive and not totally worthless, just about right for what and in what quantities they are used for.