That's a good compromise, as good as compromises now can get. I'm not sure the cost inflation is linear though. As with normal creatures, the more worth you get out of a single card, the more quanta it has to cost. However, with the current game mechanics, there are very few ways of stopping immortal damage. It's a bit like Poison in that respect.
So, the cost increase curve gets steeper the more attack it has. That's why we get 2 Immortals for 12
, but a Phase Dragon costs 13
, and it's also why 7
seems more consistent than 6
for Elite Immortal since two of those make for one Elite Phase Dragon. However, since we get more card worth out of one Elite Phase Dragon, Elite Immortal should cost less to be worth the card space just like two Immortals cost less than one Phase Dragon for the same total attack.
A more general problem both Immortal and Elite Immortal suffer with is damage reduction and CC shields. When you plan for immortal damage, you need to 1) keep your total damage potential relatively high so that your stalling isn't for naught and 2) make sure your damage stays like it's supposed to. Otherwise you will fizzle out. Thanks to the current game mechanics, this gives Phase Dragon even -more- card value as it has higher attack and more HP.
If we assume Phase Dragon is balanced (it seems to be in the current environment), the cost equation is as follows:
8 attack +2 (Immortal) +1 (HP > 5) = 11
The equation for Immortal: 4 attack +2 (Immortal) = 6
Phase Dragon ends up at 11 cost, but has to cost more since its worth is greater in card space. The scaling seems to be +1 cost for each 4 attack. Similarly, if it had 20 attack, the cost would have to scale enormously. The more attack, the more card worth. Of course, there's a practical limit to this as well. Something costing 20 quanta rarely gets to come to use due to the tempo of the game.
For Elite Immortal:
5 attack +2 (Immortal) = 7.
7 - 1 (for lower card space value) = 6.
This means we get 10 attack for the cost of 2 cards (Elite Immortals) and 12
, whereas Elite Phase Dragon would be 10 damage for 1 card and 14
. Elite Phase Dragon maintains the +2 cost for card advantage that Phase Dragon has, and Elite Immortal becomes more useful. I think that's about as close to balanced as it gets when the fact is that immortal damage is more useful when condensed into fewer cards.
The question is.. is there a way to increase the attack of unupped Immortal and balance the cost? I've tried, but it becomes unbalanced with either Phase Dragon or Elite Immortal. :/
Let me know if you spot any logical fallacies in my reasoning. I'm not 100% sure I'm objective, after all.