If you want headlights that work as designed, yes, upgrading the headlight wiring is required.
It's not uncommon for these mopars to have as little as ~11-11.5 volts at the headlight plug. Light output degradation from reduced headlight power inputs is not linear. A 10% decrease in voltage input can result in a greater than 10% reduction in output. A good headlight wiring approach can get 13+ volts to the headlights.