I haven't done Atmas hunting myself so I couldn't feel the pain you all are posting about.
So I read about the drop rate of Atma being 2% (I don't know where that person came up with that number but lets just base my suggestion on that number).
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The initial drop rate of Atma = 2%, and drop rate increases by 0.5% with each "Gold rank" you get with Zenith weapon equipped. The drop rate increase up to a maximum of 20%. Think of it as a "hidden buff" parameter, duration wise, 30 minutes would be sufficient. Timer resets and the buff gets +1 when you achieve the "Gold Rank" in FATE.
So to lay it out:
Initial Drop Rate of Atma in FATE: 2%
Increment of Drop Rate per "Gold Rank" achieved: +0.5%
Duration of the Drop Rate buff (Reset upon getting another "Gold Rank"): 30mins
Maximum Drop Rate of Atma in FATE with said buff: 20%
Buff resets with Atma obtained / Exiting field (If they can not reset the buff upon logout that would be great, hate to get DC'd with stacking buff on)
If we start out with 2% in drop rate, we would have 36 fates to do before getting to the buff cap of 20%. Lets just say if there are actually people doing FATEs in that area and FATEs are popping at a decent speed, you spend 10mins doing it and 5mins to get to another FATE. 15mins for a "Gold Rank". You will be spending 9 hours grinding nothing but FATE in order to get to the max buff, longer if there's no one else in that area running FATEs with you. At least you would have an "increased" chance of getting an Atma since you have actually worked for 9hrs in one field.
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Well, after typing all those up I realized there will always be players going like "oh if the buff's only 30mins, does that mean I will actually have to sit in front of the computer for X amount of time? If I need to off a load/go out for dinner/go to school/catch a pokemon then I am screwed", well darn right you are. I just realized as a developer, you can never win over every player, so just stick with the current drop rate and system so they can keep complaining about it.