This is not just a change, but a reversion of what is now a huge part of the model around which buffs are planned.
Bring the player, not the class.
A buff class would need to bring a buff which is unique, otherwise what would be the point of it.
And with uniqueness comes the same situation we had then, a class potentially becoming mandatory because of a single button they can press.
For the most part such unique buffs or skills are now brought by multiple classes.
The one we mention was exactly the same icon with no difference aside from a recolour.
The blizzard default icons do vary in more than just colour, if not by a huge amount but enough to still be different.
A symbol on their foreheads, the effect around the border of the skull, the nose and eye flames on unholy.