Well, if they're "elite warriors, scouts and specialist fighters as well as a reserve for when things get rough in a fight...chosen for their prowess and ability to follow orders." I think that 'Chosen' is a good name for them.

Essentially I think the were elevated from (I.E. chosen) the pikes, spikes, blades, wargs or even camp as exceptional members of the company. During a battle they might not be fighting shoulder to shoulder--but their efforts would be in tandem, if not solely for the fact they're part of the fighting company.

As for field tactics devolving--it's important to note that in a large scale battle victory probably depends more on the 760-so soldiers and 450-odd camp orcs supplying them that our handful of heroes. The chosen probably work to keep morale, reinforce the faltering and engage in special operations.

Probably Radush's unofficial retinue of bodyguards too...as well as a rogue's gallery of those most willing and able to supplant him in a moment of weakness.