First, here’s a cool post I wrote about movement:
Contextual Move Actions

Fourth Edition Dungeons & Dragons took a big step forward in streamlining visibility rules. Reducing cover and concealment to two versions (partial or total) and making them accuracy modifiers instead of the double-jeopardy-percentile-miss-chance they represented in Third Edition was enormous.

While preferable to previous incarnations of the rules, visibility still has enormous problems. First of all, it’s still based on an antiquated line-of-sight / line-of-effect system that has probably never worked. Well, perhaps as a shortcut or workaround, but certainly not as a robust, easily-enforced subsystem.

Cover and concealment, as an extension of the visibility system in D&D, appear to be an artifact of a much older design model based around … whatever the opposite of an exception-based rules system would be called. Wizards of the Coast likes to throw that term around, but I wonder if they know what it means.

Visibility is dependent on a number of factors the players have little to no control over: the lighting in whatever environment they’re currently in, the shape of the landscape and the opacity of any terrain features, and whatever vision or visibility powers are granted by their character features (race, class, theme, etc).

Additionally we have the problem of D&D being largely melee-centric when it comes to combat (well, Fourth Edition is anyway). When designing for a game where combat may take place at close range or at a distance, it seems to me that a few systems ought to be combined and streamlined for ease of use.

Who uses Total Defense? I remember it got some play in Third Edition when combat was more deadly, healing was sparser, and the average character was less likely to be effective against a given monster, but since the advent of Basic Attacks and At-Will powers, and better balance in general, I haven’t seen it used even once. Ever.

I rarely see Second Wind used except among dwarves and the occasional warden. I understand these powers are important because they set precedents, but those precedents mean literally nothing if they never see use. No one can use them as a basis for comparison because they don’t even know they’re available.

You know what I see a lot of though? Falling prone and standing up, with the occasional crawl. Fourth Edition has tons of support for this because movement was heavily emphasized. It’s a minor action to voluntarily fall prone on your turn, and a move action (which doesn’t provoke Opportunity Attacks) to stand.

Additionally, while prone a defender gets a +2 bonus to defenses against nonadjacent ranged attacks, presumably because they represent a smaller target. I think this combination of defense bonuses and actions (Minor/Move) should be used as a basis for vision-based effects like cover and concealment.

For instance, a character might move adjacent to a “covering feature” and “take cover” to gain the bonus, regardless of the direction of their attackers. It could be a move action to do so, and moving away from the covering feature would cause the character to “break cover,” whether intentionally or by forced movement.

Concealment could be handled similarly, though since it represents a wider range of visibility, more thought should be given to its applications because achieving invisibility via concealment likely functions based on the character refraining from obvious movement. Total Defense could easily be folded into cover or concealment.

Once new rules for cover, visibility, and concealment are established, one of the long-running problems with the stealth rules in D&D can probably be built on the much more solid foundation, and the “Hidden Club” (termed in Character Optimization) can officially retire from active duty.