The advantage that Doomsphere has that Tywin and others hate to take into account is that by having control of the top tier, we've systematically gained control of all levels of the upper tier as well. Which means eventually we can down declare on all of the nations that they have and inflict more damage to their nations than they can to ours. Its a beautiful strategy first pioneered by Citadel so many years ago.
And now, with the help of alliances like Doom Squad which is full battle hardened, pipe-laying pitbulls: the upper tiers become the hammer and our lower tier is the anvil.