The cost here is probably about right, actually. (The rarity isn't.) See Vindicate and Maelstrom Pulse, Creeping Mold and Bramblecrush, and Pernicious Deed, as well as Saltblast and Desert Twister.

Yeah, it's mainly desert-twister is FAR too expensive, but a disenchant is far too useless far too often. How can I make a cheaper twister? First let's not allow land destruction (which is usually cheesy, though some land just deserves to die) and make it multi coloured...

I guess it can live at uncommon? I don't really believe in rarity as anything other than an indicator of complexity.

­Oblivion Ring is a pretty good universal answer, actually. What's interesting is that all the cards I listed above are sorceries, where this is an instant.

This could just about be uncommon. It's more normally rare, although I confess in this case I don't know why. (There are very good reasons for things like Pestilence not to be common that are unrelated to complexity, and indeed the same applies to Wrath of God and most simple Dragons / Demons / etc. But that's not really relevant here.)

Rarity matters very much in limited. Other than that, it only matters for attainability.

I think cards like Maelstrom Pulse end up as rares because of how chase the card is. Many G/B players would love to get their hands on some, and they don't print that effect that often, so they bump it to rare. It really has little to with draft and/or complexity.

In theory, and depending on your set, this card could be a common, due to the fact that it is very hard to play it in a normal game of 17 basic land magic. I certainly wouldn't first pick anything with that casting cost, unless the numbers "7/7" appeared in the bottom right hand corner.

It would still seem like a bit of a waste making this card a common, though. Unique and powerful chase instants have a strong tradition of being placed at uncommon. It gives them a sense of 'specialness', and gives players a chance to upgrade their decks from Assassinate to Putrefy or from Volcanic Hammer to Sudden Shock. In this model, instead of paying big bucks for a shiny new rare, they pay a few dollars to upgrade their removal, letting them take the first steps into the concept of refining a deck in a collectible card game.

Or, looking at this from a player's angle, there are a lot of people who like simple, yet strong effects. If all of those simple but strong effects were in common... what is there for them to look forward to as they continue to play the game?

Well, this card is just "Naturalise and Terror in a tree..." so instant seemed obviously wanted. The cost is indeed nasty, but I really didn't want it to be more than 4, or it'd be useless.

All of that stuff about rarity? That's stuff about making the game sticky and make the owners more money. None of it is about the game, or the fun. (The exception is the comment about distribution in limited)

So yeah - I recognise that it's a feature of the game. I just don't LIKE that feature, and since I'm putting together silly environment-stretching cards, I feel no need to support it.

...though now I'm wondering about playing limited in a set which has had its rarities inverted. First pick that basic removal spell or cheap creature, because you'll see PLENTY of game ending 6/6 mythics.

Personally, I think that the collectibility of the game is 'fun'. But I certainly understand why other people would consider it a hindrance, and/or outright unnecessary.

But all that stuff about rarity? It's not all about making money. Sometimes it's a means to control how often a card appears. If not everyone has access to 4x a card, then the card becomes a little special, and that seems fine. After all, if all players had access to all cards at all times, they probably wouldn't make decks due to the sheer number of deck building decisions they had to make, or, there would only be one deck filled with the best cards. While I know that rarity is how Wizards makes their money, I'm also sure that it's how the game continues to be lively.

Not, as you mentioned, that any of this is important to making your own set. If the hypothetical future of your set involves all players having a full play set, then rarity has no value.

Personally, I like rarity. For me, it has an impact on the way a card "feels." It's also a nice guideline for designing cards.