IIRC you are only guaranteed to receive loot if you do the first 3 raids (Jade Palace, Tempest and Horror). The loot amount guaranteed should be 2. (From those 3 raids)
1 loot was still guaranteed only on jade palace but have to defeat all boss, for solo ones it has always be a low rate and often 0 loot.
i do remember many weekls doing Jade palace/ Horror & Tempest and get only 1 loot from jade palace.