Cost should not be more than 5 . Either lower the base damage a bit or something. You also have to factor in spell damage can be completely countered.
And there are more ways to completely counter the purely physical damage of fahrenheit. e.g. wings, dim shield, hax shield (with insane luck)....
If your spell damage is countered, you can also adjust your
level to reduce the damage dealt to yourself.
If this card is really too expensive, the only thing I can do is to lower the physical damage for a lower cost.