II don't know what Herman's is but I've heard that a lot of agent listings aren't strictly filled with reliable agencies. Anyone with a business they call a literary agency can get a listing if they're willing to pay.
I'm actually not aware of any listings which require payment, and I'm in Herman's guide, as well as querytracker and agentquery.
Publisher's Marketplace does require a subscription but that's for the whole site, and even writers pay that to see deals and such.
FWIW, our agency (D43O) did not have a big web presence when I joined. Bob had run the agency for 23 years, had nealry 1,000 sales to every major publisher (he topped 1,000 in the last year), and did not have a website. He had a single page at Publisher's Marketplace.
But every time I talked to him, he'd just finished golfing with a vice president at one publisher and an editorial director from another. He has serious connections. He's just beenin the business so long, he really didn't need a web presence.
That said, we launched our website a couple of months ago. D43O has four newer/"young" agents who ARE building lists and actively searching through the query pile, so we wanted that presence.
But Bob does just fine without it.