I'd put Solano on the list, tbh, if only because Farune is so underperforming otherwise. But yeah, it's more of a testament that summoners are already good as a mincost event plat, rather than the plat itself being as good as a black.

And while we're including other event units, Shiho and Rika excel at their jobs, even if they don't have black-tier equivalents (on our end, anyway).