What major change are you expecting exactly? Any change is going to be "important" to the Main Scenario and simply fixed in side quests with dialog tweaks. Just because the Culinarian quest has a simple fix for a major plot hole doesn't mean it's suddenly unimportant. If Ul'dah sees significant changes and the Main Scenario never touches on it again (how many quests have we had dedicated to the turmoil there currently?) then that is due to terrible writing, not because a side quest stifled the story... Why would you even expect to see the significant repercussions in a side quest anyway? The Culinarian quest, for example, is about Culinarian, not the reformation of Ul'dah. It is about cooking a meal to impress an important diplomat. That is its focus, after 2.5 and whatever happens in Ul'dah that focus should not change. If it makes mention of the changes (similar to 2.2 and the Ninja quests), then that is great for continuity and storytelling in general. If it doesn't it's an ugly plot hole. It in no way stifles the story though...
