It does stack with Last Stand. It shares a cooldown with Last Stand, but the CD is only triggered when YOU use Rallying Cry; if you gain it from another warrior, your Last Stand is not put on cooldown.

Is it rally cry or rallying cry?

A rallying cry or rallying call is something such as a word or phrase, an event, or a belief which encourages people to unite and to act in support of a particular group or idea.

Does rallying cry affect?

Rallying Cry is a warcry skill that taunts nearby enemies and applies a buff to you and your allies that grants added damage proportional to your own weapon's damage based on the power of nearby enemies and allies.