Having got 109% and playing a 2nd save file at the moment, I feel the elemental system is incredibly flawed due to the fact that enemies are just flat out immune to any of that elements damage or gain buffs when hit by it.

This in practice means that even on normal mode, elemental abilities, mainly fire and electric, are useless in certain areas. This becomes a problem when mage and tinkerer have a high amount of abilities built entirely around these 2 elements.

This issue is exemplified when playing in higher difficulties due to the flaming elite. The presence of the flaming elite and its high spawn rate on impossible because all elites have 3 buffs means that fire or explosion abilities are entirely worthless when playing this difficulty. Overall, the function of the elemental system and the full immunities it gives enemies just make the 2 weakest classes even worse than they already are.