User blog:Blaisem/Toughness vs. Tough Body

Introduction
Hi there. I just started Zombie Assault and am playing a Heavy class right now. I'm not very high level, so some of the things might be wrong. I've done a little research, but maybe I overlooked some details or just lack high-level experience. I read about how many Heavy class players like to invest in Tough Body. To me, Toughness seemed so much better. After putting a few points into Toughness, I decided it would be good to actually plan my build, just in case there is some optimal balance somewhere. It turns out there's no balance in the math; Toughness is always favored. The question becomes by how much it's favored, and whether this value is relevant to your playstyle. Discussing this is the purpose of this post.

Background

 * Tough Body vs. Toughness
 * One might wonder at the optimal balance between Tough Body (bonus 6 + 2% Damage Reduction per point) and Toughness (bonus 300 health per point). For example, there is a difference in survivability between 5,000 health and 10% DR compared to 10,000 health and 20% DR. We can model this by assuming 26 available skill points to split between the two skills.  The trends established with 26 points can serve as guidelines for any amount of available skill points.

There are four things to consider here:


 * The difference between maximum health and current health
 * If you are usually at half health, you no longer care what your maximum health from Toughness might be. You just want to survive as long as possible. Max health is relevant if you are in danger of dying from full health without a chance to heal to full health in between ie. a swarm of enemies overwhelm you, or over the course of an extended boss fight, like in Power Out. Healing to full health during a level is ok; healing without reaching full health is what devalues Toughness.  Much of the discussion depends on how often you heal to full or only heal partially.


 * Your level and base health
 * Base health increases by 100 per level.  Getting 300 health at level 25, when your base health is 4600, is a much bigger help than getting 300 health at level 75, where your base health is 9600.


 * The effect of armor
 * Armor adds its own %DR according to the squareroot of the armor value.  Armor's %DR stacks multiplicatively with Tough Body.  A rule of thumb for adding the two is that Tough Body's %DR is reduced by a percentage equal to armor's %DR.  For example, if you have 25% DR from armor, then your Tough Body is only 75% effective, eg. 24% DR from Tough Body would be effectively 18% DR, and your total %DR would be 25% armor + 18% Tough Body = 43% overall.


 * Different types of armor
 * Likely your physical defense is greater than heat or toxic. Perhaps the most reasonable solution is to attempt to average the values.  If you expect to have 30% physical DR and ~22% for Heat/Toxic, we can approximate your performance as 25% DR.

Number Crunching
Referencing point one, survivability at max health is greatest with 25 points in Toughness and 1 point in Tough Body, even up to level 100. This is a linear increase (albeit diminishing), so there is no other more efficient way of spending 26 skill points for survivability at max health. How much greater is the advantage of 25 Toughness / 1 Tough Body over 1 Toughness / 25 Tough Body? This depends on your base health. At level 45 (base health 6600), the difference is about a 30% increase in favor of the former combination. At level 75, (base health 9600), the difference is only a 9% increase in favor of the former. This means at lower levels, Toughness is more efficient and more likely to keep you alive if you can keep your health above ~70%.

Depending on how much this threshold is valued, ie. how high you normally keep your health, ideally you would place points into Toughness while leveling and later do a skill reset to reapportion the points in favor of Tough Body. A good level to consider this is around 65, where the advantage has dropped to ~14% for Toughness. Regardless, you always want at least one point in Tough Body, because the first point grants a very efficient bonus of 6% instead of the usual 2%.

What about armor? The above numbers were calculated at 25% DR from armor. At higher values of armor, Toughness will be relevant for longer. For example, taking the 9% increase at level 75 quoted above, levels 75/85/95 become 29%/18%/17% if you assume enough armor for 45% damage resist. This a very, very high amount of armor and may only be reasonable with heavy armor augmentation as well as if you consistently play with a medic who has a high level armor aura.

Finally, Dark Minions ignore armor. This heavily favors Tough Body. Even at level 25, against Dark Minions the advantage for 25 Toughness / 1 Tough Body is only at ~25%. By level 45, the advantage has dropped to ~2%, so Toughness becomes unfavorable if you get any healing at all without reaching max health.

Summary
In conclusion, consider the following, in order of priority:

1.  Is it worthwhile to me to maximize my survivability while leveling up?

2.  How often do I die to non-dark minions?

3. At what percentage of my max health do I usually operate at?

4. How much armor do/will I have?

First question: If yes, go to question 2. If no, you can quit the discussion right now and just skill Tough Body.

Second question: If non-dark minions are a threat, go to question 3. Otherwise, skill Tough Body.

Third question: If your health going into a boss fight is usually around 75% or greater, raise Toughness. This threshold becomes higher as you grow in level. By around level 75 it's over 90%, so a skill reset is probably in order.

Fourth question: For the very rare player, if you expect to achieve high amounts of armor eg. greater than 1500, probably through Medic Aura, then raise Toughness, unless you think you'll still be usually at half health or lower. It should be noted that this is an exceedingly high amount of armor and would require high quality defensive equipment and prioritizing defensive augmentation over usually more desirable utility/offensive augments. The exception is if you play very often with a medic who is maxing their armor aura.

In any case, at least one point should always be in Tough Body.