FOA Warlords are the only option available for a flying character, which at least has its uses. But aside from that you’re right - there’s not really a good reason to take a Warlord in FoA.
Actually the Commander options for FoA aren’t much better from what I can tell. Warlocks are very expensive for a Spellcaster and the Efreet lacks Inspiring. The Despoiler/Cardinal have potential as a Large Infantry face beater, but they have the same challenges all melee Heroes do in 4th, which make them tricky to use well.
I know which Command Orders Undead have and for which units. I have an Undead Army myself. And several others, which all have the same problem - command orders often suck, because they work on only few units. But where’s the problem? And I wrote that it is still possible and probably useful to take shamblers.
Just to have the option to take a Vampire and switch slots is way better than don’t even having an option for that, like FoA. And by the way - there Command Orders quite suck imho. Better defense against shooting on big, cheap units with Regeneration is needed for nothing, because nobody will shoot them anyway…
And Fireball - 12 inch is so short, the damage is not impressing.
I don’t know, I’d like a Warlord who does something like the Fire Elementals > Brutes, what if the Vampire Lord on foot buffed Soul Reavers? That would motivate me to take them!