With Sangamori the Possessed camo or any camo from rainbow keys, I think the drop rate is abysmal. 400% won't help you. It's a "you gotto get lucky" drop, no amount of rdr will help you. Do some people get one? Yes. Will it be you specifically? Probably not. Rainbow keys even have some camos that don't and have never dropped elsewhere (they did on jp but we never had the quests).
I personally think the 400% rare-drop rate buyable ticket for AC should outright not exist, BUT if it has to, I'd say bump up the drop rate to say... 4000% to warrant the price (and I'm still not sure if this would actually help you). If you do do spend the money on a free game, in my opinion, yes you do deserve all the things as you said. As of now I do agree the 400% rdr ticket is a scam. I'd spend your AC on scratches instead, at least then you'd get items worth the meseta to actually outright buy your item.
Maybe if Sega hosts the Death, Destroyer of Worlds limited quest again, maybe that'll allow you to get your camo. You can still play the quest with triggers. The trigger host gets a 100% higher rdr, you'll need 3 other people though. There's a camo I want the Sorcerer Morus that ONLY drops from Rainbow keys period and we never have gotton the quest that normally drops it (drops from 2 limited quests we never got, Trial of the Epoch: Excluder and Special Breakthrough Training: Episode 5). Goes for 300m+ and that's when it's even listed!