And it would not confuse a player because it only needs to be implemented, and players do not need to know how it is calculated. All they need to know is that having more makes it harder to hit them, but it will always be possible to hit.
I agree and disagree. ScaredGirl or someone mentioned something a while ago, along the lines of, if we keep implementing 'random' or % based features in the game of elements, soon we can reduce it to flipping a coin to decide who wins or loses. Now, that statement was meant more as a flame against purely 'random' things.
But, I can assure you, a lot of people will want to know the exact numbers, the chance to miss, etc. For example, what would be the card text of a Fog Cluster? "Causes attacking creatures to miss"? "Causes some attacking creatures to miss?"
My suggestion is that it is changed slightly,
Fog Cluster
Permanent (Until start of your next turn - like a half-sundial)
Ability: Causes 15% of opponent attacks to miss.
Notes: Stacks.
That way, with the maximum of 6 in play, you have a 90% chance of avoiding all damage. Then, the 10% of attacks that get through will then be subjected to your shield, ie. 40% chance to miss. So it will be two sort of to-hit checks.
But this is how it works with Sundial anyway. No creatures attack, and therefore no creatures are affected by your shield. A weapon still attacks, but if you have Titanium Shield, then the weapon damage is reduced by 3.
So, Fog Clusters will stop as many attacks as possible. Then, the remaining attacks that get through will be affected by your shield, ie. Fire Buckler.
The balancing of the card is such that if you eventually get 6 Steam Lords in a game, it will be very late in the game that a 90% chance to miss on incoming attacks is a valuable thing to have. But in most situations you will only really get 2 to 3 Steam Lords in play.