Some sort of sound could be added to de-buff spells pre-cast that could allow for more quickly timed rebuffing.
Currently the only clue that you are being de-buffed is visual / could easily be missed. (PPU behind a wall etc)
In most situations, higher visual awareness can save you from things such as de-buff into burst of specific damage type.
It could be nice though to have audible as well as visual ques that these types of spells are coming though.
Sound could be the same for every type of de-buff spell, causing you to use visual awareness to find out what type of shield is about to be de-buffed / who it's likely aimed at. (Triple shield de-buff (don't remember name) could be different.)