Your math is correct when calculating a specific prim, for ONE person. But there are multiple set to that rarity. So that increases your odds by quite a bit. (Not to mention the chance for it to drop per kraken fight, is better than the chances to drop for just 1 person)
The chance system works similar to how Jolly Aura's roll on Santa fights, those are at a 1 in 300 base though.
Snowballs are a 1 in 512 base.
Their chances are a bit on the higher end, but I still think it's fair, seeing as the base drops are very good for a 10-15 minute boss, that 32 people can join in on. And there's an entirely separate drop table (enraged eyes) you can access with the much more common eye drop.
But in the end, it's always better to make something TOO rare, rather than not rare enough at the start.
The chance system works similar to how Jolly Aura's roll on Santa fights, those are at a 1 in 300 base though.
Snowballs are a 1 in 512 base.
Their chances are a bit on the higher end, but I still think it's fair, seeing as the base drops are very good for a 10-15 minute boss, that 32 people can join in on. And there's an entirely separate drop table (enraged eyes) you can access with the much more common eye drop.
But in the end, it's always better to make something TOO rare, rather than not rare enough at the start.