I think in this case, that the phrasing "decapitate" is more a metaphor than an actual skill. I haven't found a unit that has a skill named that, so I don't think that is the case.
Additional, i dont fully agree with the claim. Yes, you could to some heavy start nuking with some combos, but then it's a question of counterplaying it in your own lineup.
A lineup poised on striking fast and hard often have little room if they dont succeed in that first strike.
Having said that, some characters and units in Diskwars ARE a bit out of balance, but that's just my opinion.