A-ah, the dragons...
The only thing I can tell about splitting acid is that it heavily depends on Stamina at the momemt it is ... well ... splitted.
The more stamina dragon has - the heavier damage will be.
But it's rather a percentage of remaining stamina that impacts how much HP's an enemy will lose.
Level may impact but not as much.
So you shouldn't expect just to blow off enemy by a high level dragon-fighter, without ... a spellcaster/bard or another dragon
.