Custom Card Game Design
The natural tendency is always to take a flat power level as the starting point for a card. After you figured out what a card is supposed to do, you try to find a fair level, where it is playable but not oppressive. But some cards, even commons, have to be pushed above this mediocrity to make for a more interesting limited environment. If there can be no premium commons or uncommons in a booster pack, there’s just no excitement in looking through it. It is inconsequential which colors are open and which card you pick.
Of course, there is a limit to how powerful a common should be. They show up very often and can warp the limited format around them. But uncommons can and should sometimes be pushed to bomb territory. But still, I find myself hesitant to do so. Only after a few test drafts of Overworld I realized that the power level of the cards is far too homogenized.
In a blog post, Wizards stated that they intend each uncommon to be below the power level of Mahamoti Djinn, which is an odd benchmark to set considering I can think of a handful cards just off the top of my head that violate this rule: Cone of Flame, Elite Scaleguard, even something as simple as Serra Angel. Even if Mahamoti Djinn is a bit low, the limit should be somewhere below Cone of Flame or Elite Scaleguard. They often just win the game on the spot, which I think an uncommon shouldn’t be able to do.
The sheer power of an uncommon is not be something that should be pushed that far. That is what rares are for. Build-around cards are maybe an exception and can have game-breaking effects at uncommon if they support or enable a unique draft strategy. A good example for this is Angelic Accord. On the other hand, the efficiency of uncommons can be pushed without worries. In Overworld, I tried to do this for at least one card of each color. None of these uncommons are game-breaking, but they are still great, first-pickable cards.