Currently Frost DK are doing more damage in single target using a 2H. This is bad for the game because all the Frost DK will want 2H weapons, further contesting a pool with already a lot of other specs. They should be wanting to use 1H strengrh weapons, being the only dps that can benefit from them, and only having slight competition from 2 tank specs.
2H is meant to be viable so people can use Frost as an off-spec, but it shouldn’t be better than Dual Wield.
This also enforces a style where you have to choose if you want to be good at cleave or single target, which is not good.