Too weak mobs can be fixed to work with trials simply by modifying the exp system to give at least 1 exp for too weak mobs at least level 50. If a mob is level 50 or higher no matter what it rates it should give at least 1 exp to each player. The work SE is doing seems to be one of those complex over thought out systems. Reverting the old system while maintaining the exp boost and giving a base +1 to +5 exp bonus for level 50+ would've solved the issue completely.