A totally different approach comes to my mind:
Mark for an ability:: Draw a card
Attack with side effects:: Deal 2 damage to any defending unit
(which is the same image upside-down)
This is just an idea. My icons (which aren't the right size yet
) do not indicate the turning of cards but the action that is going on in our virtual game world. An uprised sword is a common image for attack. A lowered sword means that the unit is currently not attacking, but it may use some other abilities. Because attacking and the usage of abilities are usually mutually exclusive, a mirrored image can be a good choice.
This is just a suggestion. I'm also okay with the other mark symbols you have posted.