Event Chest Rewards Far Under Par

Thanks to leveling a paladin to near 50 (lvl 48), I’m now able to regularly complete the Daily Siege Event battles that my level 50 (43) necro cannot complete. This gives me access to one or two chest rewards, iron and gold level. The mobs presented in the Tier X battle are level 40-42 minibosses, gear scores above 1800 (still “green” for my 1622 gear scored pally). However, the chests opened have exceptionally low-leveled loot though, typically minor shards, and only 2-3 slots. This seems far below the level of loot one would expect, as a level 37 skirmish (3 non-boss mobs) delivers greater, and sometimes major, shards, for appx. the same level of effort. Is this a bug or expected behavior?