I DMed for a game with a Warlock from 3rd to 12th levels. She mainly used Hex and Eldritch Blast for offense, keeping her other slots for counter spell, blink, Misty Step, and the occasional hellish rebuke. The Battle Master Fighter outshined her in damage, but her ability to shut down enemy spellcasters was bar none.
To adequately compare Warlock EB+Hex damage, I think the other warlock slots need to at least be dumped into hellish rebuke or scorching ray. A scorching ray up cast with Hex is a scary thing.