“7 mana cost, common colorless spell, gives +2/+2 to target creature”
This card was perfectly fine… until Murderer’s Axe came out, which is exactly the same except it costs 5 mana. Now there is absolutely NO REASON to use Chitinous Cloak unless for some reason you are so unlucky that you can’t get a Murderous Axe (which is really just a matter of time).
Some suggestions to fix this:
Buff Chitinous Cloak in some form
Make Murderer’s Axe color specific (e.g. black)
Make Chitinous Cloak uncommon (bad idea IMO)
Remove Chitinous Cloak from the game (1 less possible common card to get in a booster)
Implement a game mode that restricts the card sets you can use in a deck (e.g. BfZ cards only)
Chitinous Cloak is already uncommon. (It’s from OGW which doesn’t have commons.)
Which, hey, gives you a reason to play it - once you master it, you get +2 to every colour mastery, rather than +1!
(Although it takes you twice as long to master it, so it rather balances out…)
I thought the exact same thing today when I finally got Chitinous Cloak but then I realized that this will be more and more of an issue in the future. Of course there will always be strictly better cards because otherwise they would run out of design space pretty quickly and the power level would become weird. Although, the problem is different here because up to now, cards don’t rotate out. And on a positive note, try to see it differently. Now you have two different cards to pump your creature permanently. I think it’s important not just to see it on a simple “One card is better than the other”-level.
Oops sorry, my mistake. I thought it was a common. I mixed up my cards earlier, but the idea was that Murderer’s Axe should be rarer than the Cloak since it’s the strictly better card.