So, given that A) I never played 4E so I was never at a table where the 4E version was played and B) there are some negative real-world connotations to the word "warlord," I think I'd avoid it. As I understand the concept--martial class that passes actions to others and/or improves the efficacy of others' actions in combat--I think I'd go with something on the lines of "commander" or its near-synonyms (general, captain, marshall, etc.) I might avoid "marshall," since (at least in the US) that's typically a law enforcement officer.