Silent Casting is boss.
And if you get the Augmented Flames/Frost/Electricity Perks also, you can make Destruction somewhat useful again (the damage scaling for Destruction svcks
so badly...).
One of my favorite tactics is to Sneak around until my enemies are between myself, and a wall or corner of a wall, etc. Then from the shadows, I use the benefit of Silent Casting to drop two Dremora Lords right in between me and the enemies (or with them sandwiched between a wall and Daedra.

).
One minute, their day is boring. Then they die.
It's effective, and they never had the time to react really. lol