I think one big problem that there are just too few bosses and too much gear spread out over the bosses, thus creating the low drop rate many players face. My suggestion would be to put some gear exclusive to tokens from bosses that can be redeemed from an npc and spread out the remaining loot among the bosses. This would allow a higher chance of a loot dropping from a boss at the same time collecting tokens that guarantee some kind of loot as long as you killed that boss.