The description on Blizzard's site is a bit vague:
Restless Giant 20% movement speed 35% attack speed 200% Physical damage This effect cannot occur more than once every 120 seconds. Elite enemies include champions, rares, bosses, and other players.
This seems to be saying that the Gargantuan will attack at roughly 1/3 of his normal rate, but do twice his normal damage. Or is it 200% weapon damage (which would be a very nice boost over the Gargantuan's normal 25% damage)?
Is this a triggered effect that occurs when you have a Gargantuan out (i.e. it has normal stats until the effect triggers)? I've heard that it may trigger under other circumstances besides the elite enemies (one rumor was that 5 or more enemies in melee could trigger it). If it is triggered, what can cause it to trigger?