hallo Ice . i have opened many chests and here some ideas:
1. its really hard to get red/purple cards.
2. red cards arent that usefull and hard to get. the red troops should be boosted a bit but the card rarity should stay as it is.
3. puple cards are really hard to get and if they come (for example in mega chest of arena 10) they most times come at a big pack like 11 cards at once. i think you should make then to apear at minimum 1 time at mega, 1 in battle and 5 in super battle chests of arena 10. and if they appear they shouldnt come more than 5 cards at once. so increase the chance to get them by 200% and decrease their maximum appearance by 50%. that should increase their drop chance for about 100% in total.
4. the upgrade costs of purple cards is rediculus low - 2500 gold to update from level 2 to 3 i think :P
5. some people think that battle chests are more worth than mega chests. that should be the reason why battle chests cost more in store than mega chests. but i opened really many of them and i can say: mega chests are much better than battle chests.
6. green cards are maxed at first (before white) because their drop chance is very high. their drop chance should be decreased or their maximum level increased by 1. but then also the maximum levels of red cards should be increased by 1. another option is to decrease the maximum level of white cards by one. i think that also could be a good solution.
7. before implement the new cards some weeks ago we discussed about cards drop chance and for example that its a bit weird to bring in new cards at level 1 because noone will use them for many weeks because all other cards are much higher. but nothing happened to that. my suggestion: you can include in the drop chance algoriths the card level. for example if you have many green cards at level 8 and a green card at level 5, you should have much higher chance to find the lower card. that would also bring a solution to another problem: if you have been really lucky with 1 card - lets say dwarven tower - and you max it many weeks before you max any other card and then you get dwarven tower cards all the time and they are transformed into some gold because you have maxed it, its a bad situation.
8. i am not sure if its true but i opened about 8 arena 10 super battle chests and never have seen a purple card in there. is the purple card drop chance there so low?

maybe you want to think about something of that and rebalance some settings.