Last two days I skimmed over all card ideas in Crucible and Forge, and some at "level 0" of development. It seems that there is abundance of card ideas with abilities that rely on random factor.
I will quickly digress here and say that I still believe that skill > random in any given situation, and yes, even more fun.
But it seems to me that people think of an idea, and then throw a completely unnecessary random factor in there to make it vaguely balanced.
Random is good if it brings fun factor to the game. For example mutation. Mutation is fun because it brings "wow" factor. It could be 0/2 quinted dive creature which will make you come to chat to laugh about it, or 12/8 dragon with steal/destroy/devour/grow which you will be very happy to see.
Random ability that will maybe do something, or maybe wont do something, is just meh. Its not fun. It could just bring frustration to its user. If you're worried about balance of your card, just make its ability weaker. Or card more expensive. Dont make it random.
On the side note, existing cards in the game are far from balanced anyway. There is a card in crucible with 0/1 stats that deals 1 damage to *surprise* random creature. While I really cannot understand why target creature really must be random, people called the card overpowered. Go figure.