I also don’t think it’s necessary to have a perfect 1:1 ratio of available units between every army. As long as a faction has enough units to fill all the roles that make thematic sense and allow players some choice in how to build their collections... But it’s more than a little silly to have some factions be unplayable due to lacking required elements (e.g., Ironweld Arsenal has no Battleline) and kind of weird to see some individual factions that have more unique name characters than several factions entire number of units.
Plus, no matter how you slice it, the fact that the Stormcast have gotten four Battletomes in five years is just ridiculous. Yeah, yeah, they’re the stars of the setting and very popular with the fans... But, c’mon, they don’t even push out [big bad swear word] for the Space Marines at this sort of pace.