There are many different ways to be an art director. It’s a wide and open field where, depending on person, project, and team-size the responsibilities differ.
Coherence: a sticking or cleaving together; union of parts of the same body; cohesion.
Art direction is about art. Your primary responsibility is about making things look good. It is a privilege to be an art director, and it is wrong to place artistic excellence secondary to technical requirements. Deathrey put it in words really well:
[…] And as for art, there is a growing trend of favoring tech over results. For vfx artists, it is important to understand the effect, feel it, and communicate it to end user. How? It does not matter, as long as you stay with constraints of the tools you have and performance consideration. Being any kind of savvy with shaders, for example, is a plus, but never a substitute for that primary responsibility. I see this trend in action on routine basis these days. An artist favored solving art problem with tech, such as making a complex material to blend enormous number of textures. Thing is, that it is actually worse, than not having great art because now they have not great and slow art. Instead, they should have focused on achieving result, but the way to it was prioritized over goal itself. Those who let go of these constraints, start improving swiftly. Easy availability of learning material and accessible tools, such as graph based editors have really contributed to it. It creates false sense of compulsion to use them as much as possible, even when there is no objective grounds to do so.
This is in line with Darren Bartley’s advice about concept art:
Technique is easy to teach, thought process isn't. And its the thought process stuff that will lead to better, more interesting solutions.
Insert here various ideas about visual identity starting with a definition.
Best of industry example: Marathon
Star Wars Jedi: Survivor Visual Identity Case Study
Daniel Dociu - This talk is quite painful to listen to but has a large amount of fundamental knowledge about art, things that are important to an art director when directing a game. The Q&A has some good bits too. Take-aways:
Guild Wars: The Artists' Vision