Just broad observations so far, pooling between TH2 and TH6 and comparing to TH0:
* Raxa Drop rate is approximately the same in all cases
* Golem Shard drop rate is approximately the same in all cases
* Diorite Drop rate is dramatically higher for TH2/6
* Mythril Ore drop rate is dramatically higher for TH2/6 (~10% -> ~50%)

It makes me wonder if only specific slots (for instance, the first two) are enhanced by Treasure Hunter. Once again, we fall into the Treasure Hunter testing trap of not knowing the item groupings for this monster. Vold, if possible could you check what the item groupings are? Like, "Can I get a Mythril Ore, Golem Shard, and Diorite off the same kill?"