Tooltip Description: Revenge has a 15% chance to become active each time you are hit. Inflict 220% weapon damage to all nearby enemies. You heal 6.0% of your maximum Life for each enemy hit.
How It Works: The skill is grayed out until you get into a fight. At some point during the battle, when you get hit (15% chance), it activates. Then you can hit the hotkey to use it, and you make a kind of spinning AOE to monsters around you....the range seems pretty small (8 to 10 yards?).
Skill Comparison: Comparable skills are Cleave and Rend.
Cleave deals less damage (max 156% when runed) but generates 5 fury per attack. And it is available all the time, not like Revenge which is only available 1 in 7 times you are hit.
Rend deals 210% damage (up to max of 271% when runed) and is on par damage-wise with Revenge. It cost 20 fury per attack but fury is easy to come by in most barb builts. And again Rend is available all the time as long as you have enough fury.
Revenge is fury-neutral, i.e. doesn't cost any fury but doesn't generate any fury either, and you have to keep an eye on your UI all the time to check whether the skill has become active. The healing mechanism is mildly interesting, and I can see it being a potential lifesaver on rare unexpected occasions, but you can't exactly rely on it. Chances are that when your life is in danger, you would have chug a pot or a health globe or simply run/retreat rather than pray for Revenge to activate to save your bacon.
Analysis: Seriously, why bother having Revenge taking up a skill slot? It is unpredictable, unreliable, high-maintenance (eyes on the UI all the time), unremarkable damage and limited range. Cleave is a better option all the time imo and Rend is also a superior choice for fast fury generating builds.
So how to make Revenge more attractive? First, it should be auto-proc, which will make it immediately less annoying. Second, damage has to go up to at least 250% unruned and maybe slightly expanded range. Otherwise, I don't think this skill will be seriously considered in most barb builds.