No it isn't. If they were any weaker than that, they wouldn't be worth using at all. Cantrips need to be a respectable use of a character's turn, not only so that wizards don't totally suck once they're out of daily spells, but also so that they can use them instead of their daily spells, conserving their bigger guns for later while still making a somewhat meaningful contribution to the fight.
If cantrips do anywhere *near* 50% of Fighter damage, then Fighters become obsolete (well, ok I'll admit that if combat spells other than cantrips are removed, it'll be ok). If you are trying to make sure that CoDzilla lives, well, you are on the right path.