The increase is 2 without a Castle/Stronghold. With a Castle, it's 4.
Ley, what was meant was that the quantity is multiplied by their HP, not just their HP. So, in a week, they accumulate 800 HP, while Champions have 600, and Archons have 500.
Well, you can discuss this endlessly... I was specifically talking about one unit, namely the Phoenix.
You say that Archons have 500 HP, and Phoenixes have 800 in a week, but have you checked which of them would win? If you're going to go that far :)
I have nothing against Phoenixes, I even like them, why? - I already wrote, I don't like to repeat myself, but I have a personal preference for the ancient creatures. :)