Are 'trick' spells viable?

[Saber Cherry]

Not only are they weak, they are short range. That's an impossible double-whammy, and I'd never use them. Consider a level 2 (+ Phoenix Power, level 3) fire mage:

1) Killing 6/20 knights at range 40, at cost 20 fatigue.
2) Briefly immobilizing 6/20 knights at range 25, at cost 30 fatigue.

Notice how one of them is dumb... This goes for most of the other spells, too. The non-lethal spells need to have (some of) a substantially lower fatigue cost, greater range, greater precision, and greater area than lethal spells to be viable, and they don't.