Creeping terror attacks directly in front and 90` to the right and left like every other targeted instant in the game.
If what you're saying is true, sever force is bugged. The only skills I can think of that can be activated directly behind you while moving are heals/bubbles/cleanses/guards/target-free aoe/mouse target aoe's (things of that nature). I know of no other targeted instant attack that does what you're suggesting.
Affliction can be used omni-directionally