Complexity and difficulty are two very different things. They are often, erroneously, used synonymously when in reality they represent two very distinct mental operations.
In this article I will briefly discuss how Complexity and Difficulty are both affected by players, and the impact they have on design and player ability.
Complexity describes a level of process that players, as humans, use to interact with the game world whereas difficulty represents the effort or energy expended to complete a task, beat a boss or complete a tricky quest.
Difficulty can very easily increase without requiring a new level of complexity, for example a boss encounter on one difficulty setting might require players to move in a certain way at a specific moment, whereas on a higher difficulty setting they would be required to do so faster.
More difficult? Sure, but it certainly isn't any more complex.
This is because the mechanic still remains in the lowest level of Bloom's Taxonomy: Knowledge.
Learning is fun, kids!
Its only when we move up the scale, into “Comprehension” that things start to get more complex.
Sure, a player knows that they need to not stand in the fire, but they also need to interpret that knowledge and to understand the consequences of hot feet and its effect on their healer's patience (pissed off healers isn't a reason to execute mechanics properly, its just an amusing symptom of failure) or to understand why half the raid blew up when they didn't move out with the debuff.
Are raid encounters inherently difficult, or complex?
This is a difficult question to answer, it could be argued that they are both (or neither, if you're a pro) but most encounters do lean towards complexity over difficulty, as when executed properly a practised strategy by a raid team that knows each other well looks extremely easy, few and far-between are the bosses that are still difficult even when done 100% correctly.
Even on higher difficulty settings, the standard model of making an encounter more challenging is to make it more complex by adding new mechanics (usually making more mechanics happen simultaneous just to mess with us) but they are also made more difficult by tuning the damage higher and making existing mechanics less forgiving.
The interesting thing about humans, however, is our inclination to make things more complex in order to make them less difficult.
If a boss performs a mechanic that players are required to react to in a very specific manner, enthusiasts will invest time and energy creating an addon that will advise and direct players to act accordingly at the correct time.
Creating an addon is an entirely higher level of complexity (arguably the highest levels of Analysis and Synthesis) and difficulty, programming an addon is a hell of a lot harder than not standing in fire by several orders of magnitude but it means that a single instance of expended energy and creativity vastly reduces the amount of effort required by everybody who uses it (assuming they pay attention to it) from that point forward.
Everyone went through this stage with their UI
Humans are good at this, really good at this, we've been inventing tools and machinery to help us do our work more efficiently for thousands of years ..but why?
Romantically, benevolence. Truthfully, laziness. Scientifically, the instinctive desire to conserve energy.
Whatever the motivation, we understand that as complexity goes up, difficulty usually goes down.
This inalienable truth is what allows players of all levels of ability to have a chance of getting raid bosses down.
Complexity actually has very little to do with ability, difficulty has a much greater impact and we can affect that to a much larger degree by changing the way that players are presented with information and how they are able to interpret it.
Players at the higher end of the ability spectrum, fast learners, will learn core concepts of boss mechanics very quickly. This allows their brains more time to analyse (more taxonomy, kids!) sub-sets of information and sort them into important and unimportant categories.
These players probably know that there are tank-specific mechanics to an encounter, they might even know what they are, but as DPS they sure as hell know that they aren't affected by them so they effectively unlearn it. This leaves more room for independent thought, creativity and above all fast-recall of the information that they do need.
Meanwhile, at the lower end of the spectrum, the slower learners are still trying to figure out how to deal with the massive wall of text they are presented with when attempting to learn encounter mechanics.
These players will struggle to quickly learn a fight due to the complete information overload they have been burdened with, denying them the critical thinking and information retrieval necessary to execute a clean strategy.
When your boss strategy has multiple subdivisions, you have a problem
And it is not their fault, whilst they might rightly be considered less-able than others it is categorically unfair to label a player as being “bad” when they are trying to learn, but struggling due to poor presentation of information. These players can perform just as well as (and in some cases, out-perform) their peers when presented with information in the correct manner.
If the challenge of selecting only the information useful to them is taken out of their hands and they are simply taught the sub-lessons (and eventually taught how to recognise and ignore those that aren't necessary), these players will find the fights much less taxing, and be given a much better chance to perform.
This adds complexity to the design process when it comes to strategy, but as complexity goes up ..difficulty goes down.
External sources traditionally do a very good job of this, but most strategies cover all mechanics out of necessity, in-game resources need to do a better job of teaching people mechanics relevant to their roles to allow players of all abilities an equal opportunity environment
By all means, keep designing deeply complex and beautifully intricate raid encounters and make them hard as hell, but if you're going to design a boss with enough mechanics to fill a novel, don't punish people who are trying their best to learn by making them read one.