Edit 2010: If you are new to this thread, it would be best to start your reading with the Entropedia entry on Evader/Dodger which summarizes this thread and two others to present an overview of defense in EU.
If you would like to help out by adding new datapoints to the plots on Evader vs. mobs, see if your Evader or Dodger level is different from those already plotted with the mob you have in question and, if so, go out and count misses and hits. There are several ways to do it; the important thing is that you repeat it enough times to be sure it's accurate.
Questions and misconceptions about the defensive skills and effects thereof come up frequently on EF. I decided to do some research and combine some good sources of information as a resource. If anyone with higher or lower Evader pro standing would like to do some tests of their own to share here so i can add the data points to my plot it would be nice, but even as-is the plot is useful. Edit: Thanks to Steffel i think there's enough data, even if not very rigorously controlled, to call this well enough. I added an additional plot with his data included by scaling and it fits a curve pretty well.
To evade is to avoid something, for example, an attack from a mob. Not surprisingly Evade is the principal defense skill. This skill increases as you use it; so, as you are attacked by mobs that do melee damage. For firearms the relevant skill is called Dodge -- you will gain that skill as you are attacked by other players with pistols, rifles or explosives, or by drones, warriors, and troopers. Ranged attacks that are not from firearms (e.g. arrows from TskTsks, electrical bolts from bristlehogs or Tezlapods) all fall under the Evade skill.
VU ~9.0: This VU changed the division between the two defensive types. Dodge now applies to ranged damage. It appears that any mob with an attack range over a certain value must be dodged, while mobs with shorter range must be evaded. While this generally means that ranged attacks are dodged and melee attacks are evaded, mobs with a long reach (e.g. falxangius) fall into the Dodge category, even though their attack is melee. Conversely, a launched attack like the acid from the snablesnots has a short enough range to fall under Evade.
Avoidance is a hidden or unlocked skill that applies to both dodging and evading. It is unlocked by reaching a professional standing of 25 in the Dodger or Evader profession.
Quickness is unlocked at level 55 Evader.
Intuition is most likely unlocked at level 80 Evader.
The Professional Standings (what really counts)
These two primary skills have corresponding professional standings (Evader and Dodger), and those professional standings are the real measure of your avatar's defensive ability. The pro. standings don't just depend on evade and dodge, however: they are a composite of several skills. Therefore, it is important to consider more than just Evade and Dodge when improving your defensive abilities. For example, jdegre's thread established the following skill contributions to the Evader professional standing:
- Evade: 25% (Dodge constitutes 31% of Dodger)
- Agility (*20): 8%
- Athletics: 14% (contribution to Dodger is just 12%)
- Combat Reflexes: 11% (contribution to Dodger is just 10%)
- Courage: 7%
- Alertness: 5%
- Serendipity: 5%
- Avoidance: 6%
The other 19 percent comes from the unlocked skills associated with defense like Quickness and hunting skills like Combat Sense. Knowing these percentages can be very helpful when trying to calculate the least expensive way to chip up to a certain level. As an example, starting from 0 skills it would take 10k levels (10,000 x 25% = 2500) of Evade alone to unlock Avoidance (level 25 Evader), but it is typically unlocked at around 3900 Evade when skilling up naturally because of the contribution of the other skills gained in the process.
How they work
Professional standings in EU range from 0 to 100, they determine when unlocked (hidden) skills are obtained, and they are the numbers EU uses to determine your success at the profession. To use an example most players are familiar with, the hit ability (HA) of a weapon (from 0 to 10) is how likely you are to hit a mob with that weapon. It is also equal to the professional standing in the (Hit) for that weapon type, divided by 10 (0 to 100 for pro. standings, remember?). To continue with the hit ability example, an avatar with 0 HA doesn't miss every single shot and with 10 HA it won't hit every time. The actual percentage ranges from about 80% to 92%. It is reasonable to assume that evading will be similar: even a level 0 Evader will successfully evade some attacks, and a level 100 Evader will still take some hits. Just how much difference a high professional standing in Evader makes is a bit hard to measure, but i did some tests to get an idea.
The Effect of Evader Level
Here is a plot of my results. There are two actual data points on the plot, one for an avatar with Evader level 0.8 and one with Evader level 27.75, along with a linear extrapolation to 0.0 and 100.0 level Evader. The experiment was conducted by wearing the same armor (pixie, which protects about as much as the minimum damage of the mob so as to decay the same every hit) and being attacked by the same mob (Tantillion mature) for a period of 10-20 minutes, followed by a careful determination of the exact armor decay per minute using the sweat/fruit method. This was repeated at least five times for both avatars.
Figure 1a: armor decay[ped]/minute taken from tantillion mature on avatars with 0.8 and 27.75 Evader professional standing with a linear extrapolation to level 100; note that progression must not be linear because the extrapolated effect is negative
The results came as a surprise to me: with a Tantillion mature, the first 27-3/4 levels of Evader out of the 100 available give a 39% increase in evaded attacks. It is immediately apparent from the extrapolation that there must be a nonlinear increase in ability so as not to cross the origin -- in other words, the linear fit is not a good one. The good news seems to be that the first levels of Evader give the most significant improvement. Note that different mobs and mob maturities might be affected differently by one's Evader standing (that was not tested nor confirmed by my experiments).
Using an approximate match by eye between my data and a scaled version of Steffel's data (see later post), i created a composite normalized plot and fit a nonlinear curve to it -- a logarithmic curve. This rather nice fit demonstrates the point made above and shows that, much like skill gains themselves, there is a continuing diminishing return as the level gets higher.
Figure 1b: approximately combined data from Steffel, normalized to relative hits/minute from a hypothetical low-level mob on avatars between 0.8 and 27.75 Evader professional standing with a logarithmic extrapolation to level 100
The relationship of a mob's hit ability to an avatar's level of Evader continues to appear logarithmic. Here is a plot of all the test data to date (2008/3/25):
Figure 1c: combined plot of known mob hit ability versus Evader level data
One common misconception about defensive skills is that they decrease the amount of damage a mob does when it does hit, an understandable confusion when considering the many traits and abilities that can accomplish this in other RPGs. It just doesn't make sense in the context of the EU system, but to make sure i measured the damage taken from a mob (again Evader level = 27.75):
Figure 2: Normalized damage from a tantillion mature in chronological order; mean = 0.75
As can be seen, the damage ranges between the mob's maximum and 50% of its maximum, just like an avatar with a maxed ability on a gun. If higher evading ability decreases the frequency of high damage hits, the average (mean) of this data should be lower than the midpoint between the maximum and the minimum damage. No such effect is seen: Evader level does not affect the amount of damage taken in a hit, only how often a mob successfully hits.
The Uber Unlocks
Quickness and Intuition are considered to be Evader unlocks, but there is a lack of information about what level is required to obtain them. Dreicc recently reported that Quickness comes at level 55. It is reasoned that Intuition unlocks at level 80 because that is the highest level any skill is known to unlock (Kill Strike is an example), and there is reason to believe that is the case. Considering the changes to the skill system over the past year, it is highly unlikely anyone new will be unlocking these now, anyway.
If you find yourself still confused or with questions after reading this, please post so that i can refine it. Thank you.