I really think the whole elemental (i.e. fire, cold, elect, acid, sonic) resist system should recoded to be absorption instead.
As it is at the moment the majority of heroic levels (pre level 20) have lost some their nastiness due to +30 elemental resists being common. While at epic levels +30 resists are trivial against the spam damage output.
I so remember the feeling of trepidation running the low heroic content and seeing my heroic life flash before me as that Kobald unleashed that scaarrrry 'Burning Hands' on my 50 hp char. Now I can dance joyfully in front of him and never feel any 'ouchness'.
On the other hand these days running epic content my average 900 hp char is virtually one shotted by an elem spell even after having +30 resist plus 120 elem protection up.
I just think Spell absorption these days would be a far better and more balanced use of resistance.
It's more a philosophical thing which I also think would improve the game overall. Seriously dancing in pool of lava with a +30 fire resist and not being burnt is not in keeping with the spirit of the genre. Absorption would simply mean you ALWAYS receive some hurt no matter the spell level. It would also mean it remains relevant and useful because it always scales well into later harder difficulties.
Just a suggestion!