I've mauled stacks of multiple Eleutheroi Gaesatae mostly by the expedient of letting them (very unsuccesfully) play tag with my Iaosatae (and sending the rocks to their unshielded sides whenever possible) with Sotaroas to add some fiery pain and some Leuce Epos and close-combat infantry for massed javelins, deterrent and pursuit. All of the buggers eventually routed (and were duly run down by the Epos) without ever having gotten into hand-to-hand combat; I think I got most of my casualties from stray 'friendly' slingstones.

The fact is, them naked buggers are supposed to form a corps de rupture as a part of a battleline with proper support. By their lonesomes they don't really add up to too much, and can be readily disposed of with militia/garrison-level troops if you know your stuff.