When I use a spell such as Revenge on my Barbarian sometimes I will get a critical strike number that is rather high. Is this number that displays the number of my critical strike on one enemy, all enemies combined, or each enemy.
Revenge does NOT do one damage applied to multiple monsters. Instead each monster has separate damage rolls which are applied to each individually. So to answer your question, that critical strike would only be applied to the one monster.
If I have a critical chance of lets say 20% and I am fighting 10 monsters, I will probably get a critical hit for two of the monsters. They will individually get whatever the critical hit damage was to them. So if I do 100 damage hit with critical damage dealing 200 damage (made up numbers). Now for argument sake lets say Monster 3 and Monster 9 have high defense and reduce damage by 10%.
The damage for the monsters would be
Monster 1: 100 | Monster 2: 100 | Monster 3: 180 | Monster 4: 100 | Monster 5: 100 | Monster 6: 200 | Monster 7: 100 | Monster 8: 100 | Monster 9: 90 | Monster 10: 100 |
What this means is that each monster would take 100 damage except for the ones it critted on they would take 200 damage. The game treats them as individual hits so the monsters with high defense get hit less.