It's fine. Let me put it this way: If crimson dragon had 24 attack when upped, you would pretty much double the cost right? Well picture this. Every turn, you basically add a devourer while not gaining quanta, and also lobotomizing the opponent. (Which is worth about the same, so let's say those cancel out.)
A devourer is 2
.
To use the ability, you need 2 love quanta, which for the purpose of this argument is equivalent to 2
Normally, with cards like firefly and scarab, generating multiple isn't a massive problem. However, with devourer, you will make your opponent lose 1, then 2, then 3, then before long he is quanta locked and can't play anything unless he wants to stop all of his own creatures. The fact that he has a choice balances it somewhat, so I figure that you can drop the cost a bit from Firefly Queen and Pharaoh. (It's also a weapon, and weapons cost less than creatures of the same power level.)
So now picture this: Your opponent loses 2, then 4, then he's already draw locked by turn 3 or 4. Maybe if the opponent has a crazy insane rush deck with 20 pillars, it might take 5 turns.
If you used the unupped, it would take 10 turns. Pretty big difference.
Cost bump to 8. That or nothing at all.
