Lady Deathwhisper is the 2nd boss in ICC.
So this might not be the most useful post out there, but not the least either. Basicly she casts a curse on you which if you use an attack or spell while its on you, that spell will get a 15 sec cooldown.
Now I did not find a way to avoid the cooldown, but I did find that if for example your flash of light is on cooldown because of it for some reason - you can still cast lower ranks of the spell! Why this isn't completly useless? There are at points very critical moments in the fight where tanks are very low on health, casting your major heal with the curse could save them and then you can continue casting lower ranks of that to keep them up.
Esp useful for paladins without all that many diffrent healingabilitys.