Funny about limitations, when you mouse over any skill and have active the item/skill tooltip you have a number countdown that tells you how many seconds you need to wait before the skill is ready to use again. You just had to apply that countdown, not this whole flashing circles.

Also logically when something isnt available why do you make it flashy? it should be the other way around, turned off, not flashy with a circle spinning. Oh man these UI designers nowadays..