Marginally useful??
Fatigued
Characters who are fatigued cannot run or charge and suffer an effective penalty of -2 to Strength and Dexterity. A fatigued character becomes exhausted by doing something else that would normally cause fatigue. After 8 hours of complete rest, fatigued characters are no longer fatigued.
Exhausted
Characters who are exhausted move at half normal speed and suffer an effective penalty of -6 to Strength and Dexterity. A fatigued character becomes exhausted by doing something else that would normally cause fatigue. After 1 hour of complete rest, exhausted characters become fatigued.
What other spells give you -2 to STR and DEX for all your opponents (well, potentially - all within the cone) with no save?? Plus, no running or charging allowed.
Or -6 to STR and DEX AND 1/2 speed??
I'm glad they were at 5th and 7th level, because with no save they are pretty powerful.
Note, too, that the exhausted character will be fatigued until 8 hours of rest!!
And a fatigued Barbarian will be exhausted after raging instead of only fatigued.
Much more than marginally useful, though it will be situation-dependent.