I've been farming Cipactli in Tierra de Brea for about 2 months now. I have at least fought him twice a day and some days up to around 15 times. I still havent been able to get the Last Quetzal's Bite from him. I'm not even sure that he drops it but the w101central says that he does. Has anyone gotten it from him or is it even dropped by him at all?
Considering that this is a crowns wand that costs about 10,000 crowns I would say he drops it, but maybe a 1-5% chance of dropping it, maybe more maybe less.
Kyle is right, all crown gear are rare drops. I had to complete water works for countless times before i got the whole baconator set. I farmed crazed forest spirit for days to get a crabling pet. Just two examples. Keep on trying, you will get it! There are no impossible drop rates, except for one item. We all know its name: Amulet of Divine Influence