Lex made no mention of the fact that Mei was a peak Celestial Immortal elf warrior who owned, and in fact had established, an independent army which had since contracted itself to the Henali. The difference between mercenaries and independent armies was the cohesiveness and unity of an army, not to mention clearly defined structural hierarchy.
Basically, they both could be hired but an independent army was still much better than some mercenaries, not to mention that their perception was also much better owing to their loyalty to the army, as compared to the somewhat selfish nature of mercenaries.
