Sounds like a first step for the obliteration spec would be buffing frost strike then.
Improved frost strike talent could modified as follows:
Improved Frost Strike 0/2
Increase the damage of frost strike by 10/20%. Also spends up to 10/20 aditional runic power and increases its damage 50/100%.
Now the obliteration build is more competitive in single target with the breath build and uses up the excess runic power to do so.
Next step would be letting killing machine stack to 2 or 3 charges to make it more forgiving.