Dragon Pulse isn't good for anything outside of Dragons, i don't think Heatran really needs it for the coverage. Dragon Pulse's main use over HP Ice would be Kingdra, but it can't OHKO Kingdra and it should be accepted Kingdra will murder Heatran before it can do too much. HP Ice is also good for the ever present Zapdos. HP Ice will hit a good deal harder then Dragon Pulse on a non Yache Dragon it is 4x against, even with Yache it isn't too much weaker. So I have to agree with Saboros, HP Ice is a generally better choice