On the question of core clans and flow of cards to support each faction per expansion, the comparison to the CCG came up when discussing if there'd be room to support each. Its worth remembering that the CCG had a fairly fixed 150 card format as determined by the business model.
But that doesn't mean every card in that 150 was essential to driving the game forward or was considered great support for each faction. There was a lot of filler.
There's no reason to think we can't have the base factions receive good new cards every set even with a reduced total card count each expansion
This is an astute point. A good portion of the cards (predomanintly commons and uncommons) in various sets were filler and/or draft cards put into the set to meet quotas. Consider the shear number of cards that never made it into competetive decks because they did a slightly worse job than a previously released card.