The ability and desire to use any type of divination tool is a gift given by the Creator. How can it be a "sin"? To say that it is indicates that the Creator isn't omnipotent. I work with oracle cards, magic and spirit guides on a regular basis. The interest in these things was the result of a divine plan for my life and I have never felt as alive or contented. My needs are always met, I have immense joy inside of me and the love I have for the Creator is boundless. I see blessings in my life every single day...and yet I use oracle cards as a divination tool to ensure that my choices and actions are in the greatest and highest good.
If reading tarot or runes is supposed to be a "sin", it is only because that errant notion has been forced on us. You would think that if it was displeasing to the Creator, there would be fewer willing to study divination. But that is not the case at all...in fact, there has never been more of an interest in this than in the last half century. I find it ironic that mounting numbers of people are turning from antiquated belief systems to discover their own spirituality, at this time in history, and is hardly coincidental.
With that said, however, if one considers using runes to assist with making life decisions and encounters very negative feelings about it, don't do it. But one has to make that decision based on the relevant informaton at hand, not what has been preached at them with the express purpose of instilling fear.