I don't think there's really a need for it. I can see how rares can be seen as having the effect of making the game much more luck-based, but I think most experienced players are able to deal with rares in a fairly reliable way.
There are lots of cards that force the drawing of a rare, or have a high chance of summoning a rare. With my favourite deck, I win lots of games by playing rares - they're usually summoned by Legacy of Barbz though. :)
Similarly, there are lots of ways to discard or steal your opponent's rares, or rob him of the resources he needs to play them.