When it comes to the Battle for Middle-earth games, I am the maker of the Easterling faction for each one. That said, I have made extensive amounts of undeniable progress towards this end goal.
Of the infantry units that the Nomad Elder can summon 20 of in 1 cluster with the sound of an Easterling war horn, these guys are the third option. And they, are the long-range option of the four thrall options, three of which are infantry.
Coming soon: The fourth option is a cavalry version of this whose horse wears only a saddle and reins, which I have not gotten in-game... Yet.