Overflow servers are created when the zone or world you're attempting to join is full. They're basically just another zone instance that's made. When you try to join a world/zone that's full, you will automatically be placed in an overflow server. You can earn XP and other rewards as normal on an overflow server, and it will consider you "in queue" for the "main" zone and once space opens up, it'll ask you if you want to join the main zone.
You will receive 3 options when the main server is ready to accept you:
- Travel - This will take you to the main server
- Reenter queue - This will allow you to remain on the overflow server, placing you back into the queue. You will then receive the popup again when there is room on main.
- Leave queue - This will allow you to remain on the overflow server without constantly receiving a popup to ask if you would like to stay.
Additionally, if you let the timer on the popup run out before you make a choice, it will default to "Reenter queue", leaving you on the overflow server, which will give you a chance to leave later.
Level downscaling will downlevel your character to the maximum allowable content level for that area.
So this will affect all your primary stats, Toughness, Vitality, Power and Precision. When you open your hero panel you'll see your main stats on the right in white, and next to them on the left you'll see your 'effective' stats in green. These are the numbers that you're going to be using. As these numbers are changed this will effect your damage, hp, crit chance, etc.
The thing with you feeling more powerful is that you still have the higher level gear. So for example, if you are lv30 you might have an amulet with +11 power. You go to a lv10 area, and fight with players who at lv10 can't even equip an amulet. Now I'm assuming, but let's say that the downscaling is a %, then your overall stats will be higher, meaning you'll be stronger at lower level because of your better gear.
You are by no means at all invincible, but you'll certainly fare a little better due to having more or better gear. The real killer is that as a higher level you will have traits and skills available which lower levels will not. You can also use your Elite skill still, if you've unlocked it. So there are some advantages to revisiting the lower level areas.
I think most people's experiences of this will be doing each of the race's starter areas once they've finished their own.
You can read more on the wiki, http://wiki.guildwars2.com/wiki/Dynamic_level_adjustment
Character level adjustments have a limit, however. The
level-adjustment system won’t let a level 1 character go head-to-head
against a level 80 character with much chance of victory—a level 80
character is still going to have more bonuses on their gear and access
to a full complement of utility and elite skills that players just
don’t have at lower levels. This is not to say that the high-level
character will one-shot the level 1 player, but they will have a clear
advantage.
http://www.arena.net/blog/mike-ferguson-on-guild-wars-2-world-vs-world
Edit
Since Jan 28th 2013, the downlevelling has changed. https://www.guildwars2.com/en-gb/news/dynamic-leveling-adjustment/
Best Answer
Edit: Ignore completely what I wrote previously - I was going by how I normally read effect descriptions and by what I remembered from using it in WvW a long while ago, but in this case it seems to work completely differently from I would have expected. I'm not sure whether the description on this skill's tooltip is incorrect (wouldn't be the first time that happened) or whether my initial interpretation of it was just way off.
Simple enough to try out, and I finally took the time to do so. The effect lasts for 6 seconds each time it's applied, but, strangely, it seems to be re-applied every 3 seconds, starting about 3 seconds after the spirit is created. It almost seems as though the "skill" of the sun spirit has a 3 second cast time, and it keeps casting it. Hovering over its affect description while in the vicinity of a sun spirit, you can see that it keeps cycling "5s... 4s... 3s... 5s... 4s... 3s..." (i.e. 5.99s -> 3.0s countdown) until the spirit dies, then (again no idea why this is the case) about 3s after the spirit dies, you get the final 6s (5s, 4s, 3s, 2s, 1s, 0s, gone) of the effect.
While affected by the spirit's boon, I was able to inflict burning on my targets within very few hits; switching targets right after applying burning, I'm relatively certain I was able to inflict burning again within less than 10 seconds, but I could be wrong on that one. I also haven't had time to confirm with others whether the cooldown is shared, but will attempt to do so later this week (when my workload allows).
If anyone can confirm or expand on this, it would help to let me know I'm not going crazy, as the way this works is very counterintuitive from what I've come to expect about how to read skill descriptions.