I made a few improvements to the design of the macro. Healthstone will accept any modifier key to be held. Mass Resurrection is set as the default action and runs if out of combat and no enemy is targeted. The Icy Touch/Plague Strike sequence should reset when you drop out of combat.
Code:
/castsequence [combat,mod] Healthstone; [combat][harm,nodead] reset=combat Icy Touch, Plague Strike; [harm,dead] Loot-A-Rang; Mass Resurrection