I don't think it would be all that useful to apply historical mercenary groups to this Orcish one. The most renowned Mercenary group of the middle ages was only known as such because they refrained from running away from every single fight, though the majority of the time they sat in the middle of a bidding war without fighting anyone. The main difference here is that although we would definitely be after gold, Orcs -like- to fight, unlike the vast majority of humans. So our motives and values are going to be a lot different. Humans may be perfectly happy to slaughter a village of defenceless peasants for free easy gold, but would Orcs? Not necessarily.