To my knowledge, the power of a specific unit in clan/faption wars is calculated using this formula: 10 + 10 x 1.45P (p = number of promotions)
My question is: "why is it exponential?" Because promotions are random, the exponential formula actually punishes players who have more heroes.
What I mean is, if I start an account right now, and I never purchase any additional heroes, and I play for a year... I would actually be significantly stronger in clan wars than a person who started an account at the same time, and purchased every hero pack that was offered to them. If you only have 39 heroes, then your promotions will be significantly more concentrated than someone who has 160+ heroes, so you actually wind up with an exponentially stronger total power in clan wars when you have fewer heroes. How does that make any sense?
From a gameplay perspective, having more units in a war should help me--not hurt me. And from a business perspective, the things you're trying to sell me should help me--not hurt me. As it is right now, I wouldn't even want a new hero for free, because all it will do is soak up more promotions and slow down the rate at which I can gain clan power. So if I wouldn't even want it for free, then why would I pay for it?
When I started playing this game, I always bought all the hero packs that were offered to me, because I thought it would make me stronger, and I like to collect waifus. But ever since clan wars got released, I strongly regret it. I feel like I basically ruined my account by buying all of those heroes. Any time your customers feel that spending money actually ruined their accounts, it is a sign that you have a significant problem in your game mechanics.
Please consider changing the formula so that it uses linear scaling, instead of exponential scaling. That way, it will not punish the players who have more heroes (a.k.a. spent more money on your game) than others. I can't think of any good reasons why it should use exponential scaling, but I can think of several reasons why it shouldn't.