I had a lot of issues with Halsin's quest as well - Halsin needs a CLEAR dialogue line that tells the party to go talk to Zevlor. Either camping in any area should automatically trigger the celebration, or talking to Zevlor and saying "Yes - let's go." needs to automatically trigger the celebration scene.
When you find Rath's cache, it should update the quest log to something like - "I found the hidden cache that Rath awarded me. Halsin has asked that we rest, celebrate, and speak in the morning."
