Instead of making things simply darker for the sake of it (this is 100 years after the original two games), I would prefer a variety in tone. There should be some locations on the outskirts of civilization that are brighter and pretty with wildlife and local flora, but some locations should be gritty and dark and depressing.
I disagree with removing paths for attacks or spells as this is a standard quality of life feature that should honestly be present in any isometric style game.
Spells should feel different though and there should be more of a separation between characters and classes. Death animations would be a positive, especially if there is feedback in it (a fire spell burning a corpse, while sword slashing bodies).
Weapons should have different feels as well. A two-handed sword/axe should cleave enemies on death and it should sound meaty, while daggers obviously shouldn't. There needs to be impact though. This isn't necessary to make it "darker or more BG", but because it adds something to combat.
Combos should stay as well since it also adds tactics and something to gameplay. It also makes a bit of sense. Someone covered in gasoline will logically go up in an instant compared to someone who isn't, while someone being shocked while covered in water will take more damage than someone who isn't (look at electric chairs).
