In Guild Wars 2, you are able to revive other downed players and pets/NPC allies. To revive someone, you channel the revive skill and as you channel the skill, the person or animal you are channeling revive on gets ticks of health back until the revive bar reaches full. When it reaches full the person or animal is revived with half health.
I noticed that on different occasions the health ticks to revive someone is different. Sometimes it takes only a couple seconds to revive while other times it takes up to 20 seconds or so. What affects how fast you revive someone?
Revival and it's speed is based on several factors:
Your health when you are reviving someone (Faster when you have more health to give)
Your experience level (More Experience = More Health to start with)
The number of people helping to revive the downed player (Revival is the sum of all people working to bring you back)
If the player you are reviving has a "downed penalty" (Slower recovery time and reduced per person revival
A player will "Rally" when 25% of their overall heath has been returned to them either through player revival or other skills. You also gain a little experience for reviving someone.
The easiest way to see the difference starting with more health makes is to head to PvP and do the Revive a Player Heart Task. Since you are automatically set to level 80 when you enter you can see the per second revival stat at it's maximum vs when you go back to PvE and it adjusts to your Health/Experience combo.
The Revival page on the wiki talks to the process but not so much the exact per second calculation.
My experience was that the time taken to revive someone was standard, and the only way to do it faster was to get a second person helping. I also found that the amount of HP trickling in per tick was scaled off the max health of the target being revived. Some things got 50+ a tick, some lowbie NPCs got 5-7.