My experience in Siaulai missions is that drops and damage ranking correlate. If there is a damage ranking then there are drops. If there are no drops then there is also no damage ranking.
The same hereā¦
Silute serverā¦
Sialuais missionā¦
No silver, no XP, no Boxā¦
Guys donāt worry. I heard from a source that IMC is releasing a new token called Platinum Token where it guarantees 100% silver + cube drop and exp from killing bosses at instance dungeons. TP is all you will need for 100% drop. 
On Silute server 2 mercenary missions on Siaulia via auto-matching, both without cube nor silver.
After the first one I use the check integrity function of steam, it found 3 bad files and replace it and there was nothing wrong on the second checkup I did.
Then I did the second mission and it was the same, no silver nor cube.
Same issue on Fedimian ever since last patch. No Gold/Loot drops from Bosses in Siaulia Mission. Joined the party via the matchmaker.