So in the Gameplay Trailer we got to see some magic and spells in action for the first time, as well as some artillery, gunfire and explosions.
In my opinion, the spells looked underwhelming from a visual standpoint - at least the Bad Moon spell and the Comet - and this was mostly down to weak and underperforming lighting. To me, the spells looked more like explosions of paint and dust than real fire or energetic discharges. Making fire and explosions in Total War look luminous enough has always been a bit of an issue (personally I think Napoleon did it really well, but even then the gunfire flash was minimal compared to the orange flame decal), but I think the issue is being accentuated by the ambition of CA to create a uniformly 'grimdark' visual environment (at least in Blackfire Pass). This however comes at the expense of contrast, something that secondary light sources such as explosions could contribute to.
If the luminosity of or intensity of light from spells and gunpowder detonations were increased, these features would help make the battlefield look more alive than a pool of greys and browns. Magic and gunfire would pop out and distinguish the action on the ground for the player. Right now, it might even be difficult to notice that a spell is going on, and where (already a problem in Attila, in my opinion, with fire and fire arrows).