If we use that Sky Blitz as an example, I can use it in any deck with any mark, as long as I can pay that 9 
. This card however forces you to use one of the 3 marks, which seriously limits my options, seeing how important a mark is in a deck. I guess it's a matter of an opinion, but I don't think a card should ever be limited to 3 marks only.
I also agree that this it not unique enough. There are many ways to destroy permanents. I'll throw in one random idea.
What if this card weakens all the opponents permanents? And when a permanent is weakened, it can be destroyed by any attacking creature. So basically permanents would turn into pieces of Bonewall. They would still function as usual until they are attacked. It would fit the theme and make this card unique.
Just an idea. 
I understand your point, I guess I see this a different way. This card belongs to three elements, so for example, it can be used in a life/gravity duo, a water/time duo, and an air/aether duo. Sky Blitz can only be used in the air/aether duo. Natural Disaster will only fit in the three aforementioned decks if the mark is life, water, or air. Because of this it will only work in 3 out of the 6 possible combinations. (Life pends and gravity mark is one combination, gravity pends and life mark is another). This is your definition of limited, in which it will only work in 50% of the decks. Sky Blitz will fit into 2/2 decks, which is 100%. Therefore Natural Disaster's mark restriction limits decks while Sky Blitz does not.
My definition of limited: Of the six deck combinations mentioned above, Natural Disaster fits in 3 while Sky blitz fits into 2. Natural Disaster is therefore more versatile because it fits into more decks.
Like, you said, it's opinion based.
Also, your idea is pretty cool, I'm not going to use it because I like to think of my own cards (no offense, I do think it's a nice, unique ability). Back to the drawing board.
but the point is that I’m increasingly annoyed of the game imbalance, and nothing is being done. There comes a time when fixing the game is more important than creating a card following the strict and binding rules of the community.
Lots has been done.
We have discussed and investigated the problems.
We have identified where our preconceptions are distracting. (PC is not needed. Responses to permanents are needed.)
We have made many card suggestions many of which (like Vines) are high in the poll system.
I agree that the rules that govern what makes a card valuable to EtG do outrank the rules imposed by the community. However you might want to reread the comments. Most of them were talking about characteristics that impact the value the card would add to the game if added.
Sidenote: It may have got lost in translation, but I meant restrictive for an other card (like a shard) when I was commenting on it in the CardDesign chat.
I do agree that things are being done on the forums (which is good); however, I meant nothing is being done in the actual game. (I don't blame you for misinterpreting this, my fault for not being clear) For example, the deck Scrambled Shriekers (Novas, Discords, Graboids, Earthquakes) was first introduced in War 1. From then on more people began to use decks featuring those four cards. Now it's more than a year later, War 4, and the same deck is STILL effective.
http://elementscommunity.org/forum/index.php/topic,34088.0.html. Because it's one of the most popular decks in BL, war, and pvp events (see TPvP), something should be done to reduce it's effectiveness so other decks will be used more, and players will not have to create a specific counter deck just to attempt to beat one deck.
