Seriously.
I can't even count how many times my Rogue has been at like 300 health with a DoT on him, we're both LoS the other team, he has weakened soul, and I have time to use an instant before he dies. However, none of my spells can save him.
You have no idea what I'd do for Swiftmend, Nature's Swiftness, Riptide, or Holy Shock.