I don't have a video or a screenshot the moment it popped out to prove it, but I just recently got it, 2 weeks ago more or less. What you are experiencing right now is the same thing I've experienced. I thought its gone/unfarmable since they remove the related quest for it if i'm not mistaken. The time I got it, its only the spirit veil and no healing tonic but same box. Maybe its drop rate is really low. I think the Infinite Challenge is the one that is no longer dropable. Before, when you do dreadtide arena, you get tags and when you kill Naksun there was a high chance to get dreadtide necklace and soulshields iirc, but now Naksun only drops tags.