this Orbs only work if you are already dead, so you can't cheat death. It only spares you the time you need to run back to your location from the nearest waypoint.
what they do:
If you are defeated, they put you back to the downed mode. You are still vulnerable in this mode and if any enemy hits you, you're defeated again. So it would be wise to only use it if there are no enemies left in the area, otherwise it's like throwing your money out of the window.
Quote:
Originally Posted by Colin Johanson (Please note: the ressurect orb only puts players into the downed state and slowly gives them back health, in a dungeon this means if there are any mobs nearby you will be killed again long before you can ever res, preventing this from allowing dungeons to be progressed easier by spending $, since dungeons require a specifically player skill to overcome. If there are not mobs nearby, you could simply use the nearby res shrine. This is simply a convenience item to save time on the run back from the res shrine if you wish to do so and has no effect on power or game-balance.)