Here's how I see it: The players have no recourse to the rules as they are the domain of the DM to use as he or she pleases to serve the game experience. A player does have recourse to the DM's rulings in the exact or substantially similar fictional situations. So if the DM has ruled that dispel magic will break the succubus' charm, when the players encounter another succubus or perhaps an incubus, then they'd be right to expect dispel magic is going to work.
This doesn't logically follow. If the DM isn't beholden to the rules in the book, then why should he or she be beholden to prior rulings?
From the player perspective, both situations are identical - you think you know how things are going to resolve, based on your prior understanding, but the DM decides to do it differently and you had no way of knowing this beforehand. As a player, you're essentially flying blind, because you have no basis for guessing how any action will resolve. And with no way of knowing that, you don't have enough information to decide which actions you should or should not take.
How I see it: The DM is in charge of the rules, and can feel free to change or enforce (or not enforce) any rule as he or she sees fit, with the goal of encouraging fun. Encouraging fun
usually means that the DM should be fair, so that the players can make decisions with reasonable certainty over whether an action will automatically succeed or fail, or whether it will require some sort of check.
As such, the rules in the book form the basis for how the DM should determine whether an action is uncertain, and how to resolve it when it is uncertain. They exist so that the players will be able to understand how the DM will make those decisions. When you decide to play D&D, it's because you want these rules to form the basis over how decisions are made (and you want the DM to have the option to change things, without feeling like you're playing it incorrectly).
The DM is free to change the rules, of course, but the players should be informed of any changes long before they become relevant. When the cleric first gains access to third level spells, he or she should be informed that you handle Dispel Magic differently from what's in the book, because the rules in the book form the basis for how the player understands that the spell will work.
Every discussion on these boards, about the Rules-As-Written and Rules-As-Intended, is important because it forms the foundation for how players should expect the rules to work in play. Even consensus that a rule is vague, and open to interpretation, is valuable for establishing a baseline.
The rules won't always be clear or apply exactly in every situation. Just rule in a way that is the most fun for your group and don't worry about it.
This seems much more in line with the intent of the rule structure. Vague rules are left to interpretation, because it isn't fun to stop and cross-reference the various rules sources whenever you're uncertain. The DM is in charge of interpreting rules that are unclear, but should follow the rules in any situation where they
are clear, because the players have reasonable expectations that those rules will be followed unless you give them reason to expect differently.
