In the early days, when a spell was cloned for a different school, the animations and colors and effects where changed, so the IceZilla rampages through a winter town different from the one the StormZilla devastates. It seems now all that happens is an existing spell gets a different school label applied and, for example, Scald becomes Shadow Scald or whatever. But there is no change to the animation.
I think even a simple color filter or smoke particle effect should be used to demonstrate that the spell is not the same.
To be fair they still do this - look at all the clones of Forest Lord and Efreet for example.
I think one reason they may not go through the extra effort is because Shadow attacks used by enemies are more about game mechanics than anything else. For one players cannot dispel Shadow spells, whereas dispels used to be a common tactic for countering some boss cheats. Players likewise will have much greater difficulty reaching 100% Shadow resistance especially since most bosses have pierce. This counters another older strategy in which players would "set" to have immunity to bosses who only dealt one type of damage.
Now that being said I would love to see the Shadow-school clone attacks used by actual Shadow-school bosses and creatures get a "Shadowy" make over to give the Shadow-school a bit more of an identity instead of just reusing animations but changing the school and damage type. I love the way Shadow creatures and transformations appear wavering and translucent at times, like they are not entirely "real" or "solid". I'd love to see animations like Lighting Bugs, Storm Lord, Wraith, etc. get re-skinned to look like that when they are used by Shadow creatures.Or at the very least maybe just give them a Shadow color scheme .