i am under the impression that the words being used here are just 'vernacular'. the actual terms are Force Splitting Dancing Ballista
Splitting is bow, crossbow, arrow, and bolt only. Ballista isint on the list. Ballista =/= big crossbow.
Don't worry, you can totally just
call your Huge Heavy Crossbow a Ballista. That's what the DMG does. In fact, you'd probably be better off doing so than using an actual ballista. Heroes of Battle is pretty much just a straight nerf - significantly longer reload time, shorter range increment...
Unfortunately, you probably can't put Dancing on a ranged weapon. Or if you can, it would be fairly pointless. You'd be better off just getting an Arbalester homunculus and enchanting that.