Honestly I'm leaning more towards focus blast than HP. The accuracy sucks, but it still leaves a dent in Ferrothorn and Tyranitar, two of Dragalge's most notable threats in VGC.
Out of Fire and Ground, fire is still vastly superior. Ferrothorn is a much bigger threat in Doubles than Heatran, Fire hits Scizor hard (not sure about it's usage this year because of Intimidate spam), and it can take advantage of MZard-Y's sun in a pinch. HP Ground is basically useless; pretty much everything HP ground can hit (Heatran, Tyranitar, some steels), Hydro Pump or Focus Blast hits harder.