Friday, August 18, 2017

How squishy is Captain Nym? Comparing the durability of ships with different agility values.

I frequently see comments in the X-Wing community along the lines of:
  • Captain Nym is squishy because he only has 1 agility.
  • Y-Wings are better than TIE Aggressors because they have 3 more hit points (shields + hull).
Of course, these comments are missing at least half the picture. How long a ship survives depends on both its agility value and its hit points, along with its actions and damage mitigation upgrades (we'll ignore maneuverability, turrets, and extra firing arcs for now). Soontir Fel only has 3 hit points, but he's very difficult to kill with normal attacks thanks to his 3 agility, focus and evade tokens, and possibly Palpatine and Stealth Device. Han Solo might only have 1 agility, but he has 13 hit points and often C-3PO and evades to back it up. If you want to talk about how durable a ship is, you should at least consider both its hull and its agility, and also consider its defensive upgrades.

As it turns out, Captain Nym has comparable durability to other expensive aces without defensive abilities (e.g. Dengar and SuperDash), but he can't boost his durability as much when spending focus on defense. TIE Aggressors are less durable than Y-Wings and need to have focus on 3 defense rolls to even out.

To compare ships, I've created a durability spreadsheet. It lists the durability, modified durability (hull is discounted by 10% for critical hits), and a points-adjusted durability metric for all ships. This isn't the full picture for jousting value and it doesn't capture the benefits of pilot skill and maneuverability, but it lets you compare how ships stack up for durability alone.

If you hate math and just want to enjoy X-Wing, you can stop here! Otherwise, feel free to keep reading 🙂.


To make comparisons easier, we can use the following measure of durability. A ship's durability is the hit points the ship needs to survive the same number of 3-hit attacks with 0 agility. As an equation, it looks like this:
If a ship has 0 agility, its durability is equal to its total hit points. Ships with more agility have their hit points scaled up to reflect the lower average damage they take on each attack. The denominator can be modified to reflect any always-on defensive abilities like Luke Skywalker's ability.

As the Mynock Squadron Podcast mentioned (episode 80), hull doesn't quite contribute its full value to a ship's durability due to critical hits. I'll also use a modified durability measure which discounts hull by 10%:
Why did I choose 10%? Roughly 25% of the critical hit cards are double damage (treating Major Explosion as half), and other critical hit cards can be crippling. Only 1 in 4 hits are critical hits or 1 in 6 with focus, but critical hits are cancelled last. I think 10% is in the right ballpark.

Why should we use this? Well, I don't really expect this to catch on, but I'll explain below!

How many attacks does it take to kill the ship?

A simple way to combine a ship's agility and hit points is to see how many 3-hit attacks the ship would survive on average. Without spending focus, each green dice adds 0.375 evades per attack. This means on average, a 3-hit attack deals
  • 3 damage against a 0-agility ship.
  • 2.625 damage against a 1-agility ship.
  • 2.25 damage against a 2-agility ship.
  • 1.875 damage against a 3-agility ship.
Divide the ship's hit points by the damage per attack to see how many attacks it survives on average.

For example, let's take a look at Captain Nym. If we divide his 10 hit points by 2.625, we see he survives 3.8 attacks. For comparison, the Jumpmaster 5000 survives 4 attacks. Captain Nym is only about 5% less durable than a Jumpmaster 5000, and most of us know how annoyingly durable those can be. Of course, Captain Nym usually doesn't have the option of spending focus on defense, but he's definitely not squishy.

Similarly, we can compare the durability of TIE Aggressors with Lightweight Frame to Y-Wings. We can model the TIE Aggressor with Lightweight Frame as a 2.75-agility ship to account for range 3 and obstructed attacks. It takes an average of 2.54 attacks to kill them. On the other hand, Y-Wings take an average of 3.05 attacks before they go down, which is about 20% more durable than TIE Aggressors. Y-Wings definitely look better when neither spends focus on defense.

As an addendum, you should include always-on defensive abilities in this calculation. For example, Poe or Luke take an average of 1.8125 damage against 3-hit attacks. Thus, Luke with Integrated Astromech or Poe with a different modification survive an average of 3.3 attacks.

The usefulness of durability

Instead of using the number of attacks a ship can survive, it's often more useful to multiply that number by 3 (the damage each attack does). That gets us the durability number I mentioned earlier. It's the number of hit points the ship needs if it had 0 agility and survives the same number of attacks. Many damage mitigation options like evade tokens are only used once per turn. If we want to know how many times a ship needs to benefit from evade tokens to survive as many attacks as another ship, it's tough to calculate this using the number of attacks each ship survives. On the other hand, the difference between two ships' durability tells us how many times the evade token must be used for those ships to survive the same number of attacks.

For another example, consider focus tokens. Focus tokens greatly improve the value of green dice. With focus, each green dice adds 0.625 evades per attack, an increase of 67%. When focus is available for defense, an average 3-hit attack deals
  • 3 damage against a 0-agility ship (decrease of 0, of course).
  • 2.375 damage against a 1-agility ship (decrease of 0.25).
  • 1.75 damage against a 2-agility ship (decrease of 0.5).
  • 1.125 damage against a 3-agility ship (decrease of 0.75).
Earlier, we saw that Y-Wings are more durable than TIE Aggressors when neither spends focus on defense. How many defense rolls with focus do TIE Aggressors need to equal the durability of a Y-Wing?

To answer this question, we first calculate each ship's durability:
  • Y-Wing: 8 * 3/2.625 = 9.14
  • TIE Aggressor: 5 * 3/1.969 = 7.62
Having focus (and being willing to spend it) on a defense roll decreases damage by 0.25 for a 1-agility ship and by 0.75 for a 3-agility ship, with a difference of 0.5. Since the gap in durability is a bit over 1, the TIE Aggressor needs to have focus on three defense rolls to roughly equal the durability of a Y-Wing. A TIE Aggressor survives an average of 2.5 3-hit attacks without focus. It'd be tough for the TIE Aggressor to match the durability of a Y-Wing.

Durability for the points

Of course, a ship's durability is always relative to its point value. The Karthakk Pirate in the Scurrg (durability of 11.4) is extremely durable and only costs 24 points. On the other hand, Captain Nym can be loaded up to anywhere from 39 to 50 points, and those extra points don't improve its durability one bit.

To get a sense for how durable the ships are relative to their points, we can divide the ship's durability by its points and multiply by 100. This tells us how much durability you get if you spent 100 points on that ship. For comparison, without focus or other once-per-round defensive abilities:
  • 43-point Captain Nym gets 26.6 durability per 100 points. 
  • 53-point Dengar gets 22.6 durability per 100 points.
  • 50-point Aggressor (IG-88) gets 28.8 durability per 100 points (assuming 1 use of Autothrusters).
  • 58-point SuperDash gets 23.0 durability per 100 points.
  • 40-point BB-8 Intensity Poe gets 44.2 durability per 100 points (assuming 1 use of Autothrusters).
  • 24-point Y-Wing with Twin Laser Turret gets 38.1 durability per 100 points.
  • 25-point naked Contracted Scout gets 48 durability per 100 points.
We can see that without defensive tokens, Captain Nym is roughly comparable to other expensive aces without defensive abilities.

For the full list of durability per 100 points, please take a look at the durability spreadsheet I mentioned earlier. It also has modified durability, where hull points are discounted by 90%.

Other considerations

Agility and hit points aren't completely interchangeable. Agility doesn't help against bombs or automatic damage effects like Feedback Array or Autoblaster Turret. Hit points don't help against status effects like Ion Cannon which require the attack to hit. Ships with more green dice are also subjects to more variance than hit points. They will sometimes survive much longer than average, but sometimes they'll also die much faster than average.

Besides those specific cases, agility and hit points . Higher agility is better when defending against small attacks and worse when defending against large attacks. Soontir can shrug off a bunch of 2-hit or 3-hit attacks, but he explodes immediately if he takes an 8-hit attack from Swarm Leader Norra with Jan Ors support. I assume 3-hit attacks since the meta is trending towards bigger and more accurate attacks (3-dice attacks with focus average 2.25 hits; 4-dice attacks with focus average 3 hits). A 0-agility ship's durability will never change based on how large and accurate the opponent's attacks are, but higher-agility ships will be less durable against large and accurate attacks.

Similarly, higher agility is better when defending against fewer attacks per turn. Focus and other once-per-round defensive abilities cancel a larger percent of damage for ships with higher agility.

Finally, durability alone ignores other ways ships can stay alive. Captain Nym is fantastic at avoiding shots by arc-dodging, forcing bumps, or cutting off pursuit with bombs. Other ships like Dengar and Quickdraw avoid shots by threatening to deal extra damage to their attackers.

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