I'm just wondering if Galactus having had a dozen heralds maybe makes him look bad, because a lot of them have either turned on him or betrayed him. This happened with The Surfer, The Fallen One and Terrax, and Morg turned out to be bad. And Air Walker and Red Shift died pretty much right away. Only Stardust really seemed to work out and really have a connection and loyalty to (Maybe love?) the big G. His heralds don't seem to work out, but he keeps on making more. Can Galactus operate without a herald, and has he? I thought that there was a brief time when he did.
No, he doesn't need a Herald. Classically, he had no Herald until relatively recently when he allowed Norrin to be Surfer. Yeah, I know that's been retconned, but Ptooey!
IMO, Heralds only work as a bone Galactus threw to mortals before he ate them. Heralds are an act of charity The Big G allows because of his huge heart.
"Look peons, I'm gonna eat. So... pray, skedaddle, try to fight, or whatever else you feel you need to do."