Just a concept: what if loot scaled with the difficulty of the mob? The current values severely undermine players who fight against mobs upscaled too much because of player tagging. A good suggestion would be to add a boost on the loot chance on three variables:
The loot is scaled up even further, aside from simply tagging, by some factors:
1.) the player has tagged the monster/boss with double the values, or alternative to that, has dealt enough healing to the people in the area that are attacking the monsters
2.) the player has been at the death of the monster (I.E was there when mob died) (assume a good radius for it as well, maybe around the range of the monster’s leash/maximum strike range?)
3.) how much power/damage scaling a monster can deal.
That way, players are rewarded with sticking in a fight against the monster, and get some loot bonuses with it.